#include <cstdio>
#include <iostream>
#include <cstring>
using namespace std;
char score[101];
void init(){
        memset(score,'E',sizeof(char)*60);
        memset(score+60,'D',sizeof(char)*10);
        memset(score+70,'C',sizeof(char)*10);
        memset(score+80,'B',sizeof(char)*10);
        memset(score+90,'A',sizeof(char)*11);

}
int main(){
        init();
        int input;
        while(cin >> input)
                cout << score[input]<<endl;

        return 0;
}