#include<bits/stdc++.h> using namespace std; int main(){ int a; cin>>a; switch(a/10){ case 10:cout<<"A";break; case 9:cout<<"A";break; case 8:cout<<"B";break; case 7:cout<<"B";break; case 6:cout<<"C";break; case 5:cout<<"C";break; case 4:cout<<"D";break; case 3:cout<<"D";break; case 2:cout<<"D";break; case 1:cout<<"D";break; } return 0; }