#include <stdio.h>

int main(void) {
	// your code goes here
    int score;
    printf("请输入成绩:");
    scanf("%d",&score);
    if(score<0||score>100){
      printf("error");
    return 0;
    }
    switch(score/10)
    { case 10:
      case 9:
      case 8:
       if(score>=85)
         printf("A");
       else printf("B");break;
      case 7: printf("B");break;
      case 6: printf("C");break;
      default:printf("D");  }
	return 0;
}