#include<iostream>

using namespace std;

int main()
{
    int a;
    while(cin>>a)
    {
        if(a<0||a>100)
        {
            cout<<"Score is error!"<<endl;
        }
        else
        {
            a=a/10;
            switch(a)
            {
                case 10:
                case 9: cout<<'A'<<endl;break;
                case 8: cout<<'B'<<endl;break;
                case 7: cout<<'C'<<endl;break;
                case 6: cout<<'D'<<endl;break;
                default : cout<<'E'<<endl;
            }
        }
    }
}