View Compilation Error

0_0_25449507_10273.cpp: In function 'int main()':
0_0_25449507_10273.cpp:11:11: error: 'cin' was not declared in this scope
     while(cin>>n>>m) {
           ^
0_0_25449507_10273.cpp:20:9: error: 'cout' was not declared in this scope
         cout<<maxn<<endl;
         ^
0_0_25449507_10273.cpp:20:21: error: 'endl' was not declared in this scope
         cout<<maxn<<endl;
                     ^