View Compilation Error

0_0_39090787_27563.cpp: In function 'int main()':
0_0_39090787_27563.cpp:5:9: error: 'cin' was not declared in this scope
    5 |   while(cin>>a>>b)
      |         ^~~
0_0_39090787_27563.cpp:10:18: error: 'cout' was not declared in this scope
   10 |         { case 1:cout<<a<<endl;break;
      |                  ^~~~
0_0_39090787_27563.cpp:10:27: error: 'endl' was not declared in this scope
   10 |         { case 1:cout<<a<<endl;break;
      |                           ^~~~