View Compilation Error

0_0_37399518_8177.cpp: In function 'int main()':
0_0_37399518_8177.cpp:12:8: error: 'cin' was not declared in this scope
  while(cin>>n1>>n2>>n3){
        ^
0_0_37399518_8177.cpp:35:5: error: 'cout' was not declared in this scope
     cout<<i<<endl;
     ^
0_0_37399518_8177.cpp:35:14: error: 'endl' was not declared in this scope
     cout<<i<<endl;
              ^