View Compilation Error

0_0_29812651_32322.cpp: In function 'LL Ans()':
0_0_29812651_32322.cpp:44:78: error: 'max' was not declared in this scope
                   ans = max(ans  , (LL)(i - stk.Top().id) * stk.Top().height ) ;
                                                                              ^
0_0_29812651_32322.cpp: In function 'int main()':
0_0_29812651_32322.cpp:56:12: error: 'cin' was not declared in this scope
      while(cin>> N && N){
            ^
0_0_29812651_32322.cpp:58:34: error: 'scanf' was not declared in this scope
               scanf("%lld" ,&x[i]) ;
                                  ^
0_0_29812651_32322.cpp:60:11: error: 'cout' was not declared in this scope
           cout<<Ans()<<endl  ;
           ^
0_0_29812651_32322.cpp:60:24: error: 'endl' was not declared in this scope
           cout<<Ans()<<endl  ;
                        ^