View Compilation Error

0_0_17596234_13931.cpp: In function 'int main()':
0_0_17596234_13931.cpp:16:11: error: 'cin' was not declared in this scope
     while(cin>>n,n>=0)
           ^
0_0_17596234_13931.cpp:19:9: error: 'cout' was not declared in this scope
         cout<<0<<endl;
         ^
0_0_17596234_13931.cpp:19:18: error: 'endl' was not declared in this scope
         cout<<0<<endl;
                  ^
0_0_17596234_13931.cpp:21:9: error: 'cout' was not declared in this scope
         cout<<s[n]<<endl;
         ^
0_0_17596234_13931.cpp:21:21: error: 'endl' was not declared in this scope
         cout<<s[n]<<endl;
                     ^
0_0_17596234_13931.cpp:23:13: error: expected '}' at end of input
     return 0;
             ^