#include <iostream>
using namespace std;
int main(){
    float a; //引入浮点数a记录输入分数
    while(cin>>a){
             //根据分数大小进行划分，并做输出
        if(a<=100&&a>=90) cout<<"A"<<endl;
        if(a<=89&&a>=80) cout<<"B"<<endl;
        if(a<=79&&a>=70) cout<<"C"<<endl;
        if(a<=69&&a>=60) cout<<"D"<<endl;
        if(a<=59&&a>=0) cout<<"E"<<endl;
    }
    return 0;
}