View Compilation Error

0_0_26339264_30625.cpp: In function 'int main()':
0_0_26339264_30625.cpp:6:12: error: 'cin' was not declared in this scope
     while( cin>>n )
            ^
0_0_26339264_30625.cpp:8:9: error: 'cout' was not declared in this scope
         cout<<( n*(n+1) ) / 2<<endl<<endl;
         ^
0_0_26339264_30625.cpp:8:32: error: 'endl' was not declared in this scope
         cout<<( n*(n+1) ) / 2<<endl<<endl;
                                ^