View Compilation Error

2_33497_2826362_6673.cpp: In function 'int main()':
2_33497_2826362_6673.cpp:18:12: error: 'cin' was not declared in this scope
     while( cin >> n){
            ^
2_33497_2826362_6673.cpp:49:9: error: 'cout' was not declared in this scope
         cout << max(ans, max(ans1, ans0)) << endl;
         ^