hdoj2042 error2679

#include<iostream>
using namespace std;
int main()
{
int N,a,i,sum;
cin>>N>>endl;
while(N–)
{
sum=3;
cin>>a>>endl;
for(i=0;i<a;i++)
{
sum=(sum-1)*2;
}
cout<<sum<<endl;
}
return 0;
}
不知道为什么会这样？求指点迷津
error C2679: 二进制“>>”: 没有找到接受“overloaded-function”类型的右操作数的运算符(或没有可接受的转换)
2013\INCLUDE\istream(485): 可能是“std::basic_istream<char,std::char_traits<char>>
&std::basic_istream<char,std::char_traits<char>>::operator >>(std::basic_streambuf<char,std::char_traits<char>> *)”
2013\INCLUDE\istream(466): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(void *&)”
2013\INCLUDE\istream(448): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(long double &)”
2013\INCLUDE\istream(430): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(double &)”
2013\INCLUDE\istream(411): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(float &)”
2013\INCLUDE\istream(392): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(unsigned __int64 &)”
2013\INCLUDE\istream(373): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(__int64 &)”
2013\INCLUDE\istream(353): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(unsigned long &)”
2013\INCLUDE\istream(335): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(long &)”
2013\INCLUDE\istream(317): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(unsigned int &)”
2013\INCLUDE\istream(291): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(int &)”
2013\INCLUDE\istream(272): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(unsigned short &)”
2013\INCLUDE\istream(237): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(short &)”
2013\INCLUDE\istream(218): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(std::_Bool &)”
2013\INCLUDE\istream(211): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(std::ios_base &(__cdecl *)(std::ios_base &))”
2013\INCLUDE\istream(204): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(std::basic_ios<char,std::char_traits<char>> &(__cdecl *)(std::basic_ios<char,std::char_traits<char>> &))”
2013\INCLUDE\istream(198): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(std::basic_istream<char,std::char_traits<char>> &(__cdecl *)(std::basic_istream<char,std::char_traits<char>> &))”
2013\INCLUDE\istream(1093): 或       “std::basic_istream<char,std::char_traits<char>> &std::operator >><std::char_traits<char>>(std::basic_istream<char,std::char_traits<char>> &,unsigned char &)”
2013\INCLUDE\istream(1086): 或       “std::basic_istream<char,std::char_traits<char>> &std::operator >><std::char_traits<char>>(std::basic_istream<char,std::char_traits<char>> &,unsigned char *)”
2013\INCLUDE\istream(1079): 或       “std::basic_istream<char,std::char_traits<char>> &std::operator >><std::char_traits<char>>(std::basic_istream<char,std::char_traits<char>> &,signed char &)”
2013\INCLUDE\istream(1072): 或       “std::basic_istream<char,std::char_traits<char>> &std::operator >><std::char_traits<char>>(std::basic_istream<char,std::char_traits<char>> &,signed char *)”
尝试匹配参数列表“(std::basic_istream<char,std::char_traits<char>>, overloaded-function)”时
0_0_17738334_16798.cpp(10) : error C2679: 二进制“>>”: 没有找到接受“overloaded-function”类型的右操作数的运算符(或没有可接受的转换)
2013\INCLUDE\istream(485): 可能是“std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(std::basic_streambuf<char,std::char_traits<char>> *)”
2013\INCLUDE\istream(466): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(void *&)”
2013\INCLUDE\istream(448): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(long double &)”
2013\INCLUDE\istream(430): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(double &)”
2013\INCLUDE\istream(411): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(float &)”
2013\INCLUDE\istream(392): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(unsigned __int64 &)”
2013\INCLUDE\istream(373): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(__int64 &)”
2013\INCLUDE\istream(353): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(unsigned long &)”
2013\INCLUDE\istream(335): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(long &)”
2013\INCLUDE\istream(317): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(unsigned int &)”
2013\INCLUDE\istream(291): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(int &)”
2013\INCLUDE\istream(272): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(unsigned short &)”
2013\INCLUDE\istream(237): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(short &)”
2013\INCLUDE\istream(218): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(std::_Bool &)”
2013\INCLUDE\istream(211): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(std::ios_base &(__cdecl *)(std::ios_base &))”
2013\INCLUDE\istream(204): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(std::basic_ios<char,std::char_traits<char>> &(__cdecl *)(std::basic_ios<char,std::char_traits<char>> &))”
2013\INCLUDE\istream(198): 或       “std::basic_istream<char,std::char_traits<char>> &std::basic_istream<char,std::char_traits<char>>::operator >>(std::basic_istream<char,std::char_traits<char>> &(__cdecl *)(std::basic_istream<char,std::char_traits<char>> &))”
2013\INCLUDE\istream(1093): 或       “std::basic_istream<char,std::char_traits<char>> &std::operator >><std::char_traits<char>>(std::basic_istream<char,std::char_traits<char>> &,unsigned char &)”
2013\INCLUDE\istream(1086): 或       “std::basic_istream<char,std::char_traits<char>> &std::operator >><std::char_traits<char>>(std::basic_istream<char,std::char_traits<char>> &,unsigned char *)”
2013\INCLUDE\istream(1079): 或       “std::basic_istream<char,std::char_traits<char>> &std::operator >><std::char_traits<char>>(std::basic_istream<char,std::char_traits<char>> &,signed char &)”
2013\INCLUDE\istream(1072): 或       “std::basic_istream<char,std::char_traits<char>> &std::operator >><std::char_traits<char>>(std::basic_istream<char,std::char_traits<char>> &,signed char *)”
尝试匹配参数列表“(std::basic_istream<char,std::char_traits<char>>, overloaded-function)”时