#include<bits/stdc++.h> using namespace std; int main(){ int a,b; char op; cin>>a>>op>>b; switch(op){ case 10: case 9:cout<<'A'<<endl;break; case 8: case 7:cout<<'B'<<endl;break; case 6:cout<<'C'<<endl;break; default:cout<<'D'<<endl;break; } return 0; }