View Compilation Error

0_0_28849373_5101.cpp: In function 'int main()':
0_0_28849373_5101.cpp:90:8: error: 'cin' was not declared in this scope
  while(cin>>n)
        ^
0_0_28849373_5101.cpp:105:3: error: 'cout' was not declared in this scope
   cout << ans << endl;
   ^
0_0_28849373_5101.cpp:105:18: error: 'endl' was not declared in this scope
   cout << ans << endl;
                  ^