#include<iostream> // cin\cout\endl using namespace std; int main(){ int z; cin>>z; swicth(z){ case z/10=9,10: cout<<"A"<<endl;break; case z/10=7,8: cout<<"B"<<endl;break; case z/10=6: cout<<"C"<<endl;break; case: cout<<"D"<<endl;break; } return 0; }