#include <iostream>
using namespace std;
int main(){
    int n;
    cin>>n;
    if(n>=90)
    cout<<"A";
    else if(n>=80)
        cout<<"B";
    else if(n>=70)
        cout<<"C";
    else if(n>=60)
        cout<<"D";
    else    
        cout<<"E";
    return 0;
}