#include <stdio.h>
int main()
{
    int grade, rate;
    scanf("%d", &grade);
    rate = grade/10;
    switch(grade)
    {
    case 10:  //100分
    case 9:   //90-99分
        printf("A\n");
        break;
    case 8:   //80-89分
        printf("B\n");
        break;
    case 7:
        printf("C\n");
        break;
    case 6:
        printf("D\n");
        break;
    default :
        printf("E\n");
    }
    return 0;
}