include <bits/stdc++.h>

using namespace std; int main(){

int s;
cin>>s;
if(s>=90&&s<=100)cout<<"A";
if(s>=80&&s<90)cout<<"B";
if(s>=70&&s<80)cout<<"C";
if(s>=60&&s<70)cout<<"D";
if(s>=0&&s<60)cout<<"E";
return 0;

}