fatal error: iostream: No such file or directory

[hataiit9x]

fatal error: iostream: No such file or directory

[virusdefender]

选 c++ 语言

[hataiit9x]

选 c++ 语言
Error code 31

#include<iostream>
using namespace std;
int main()
{
   freopen ("CONGCB.in", "r", stdin);
   freopen ("CONGCB.out", "w", stdout);
   unsigned int a, b;
   cin>>a>>b;
   cout<<a+b;
   return 0;
}

Please tell me I/O file