https://old.ynoip.cn/p/1116

#include <cstdio>
using namespace std;

int main (void) {
	int s;
	scanf("%d", &s);
	s /= 10;
	switch (s) {
		case 10:
		case 9:
			printf("A");
			break;
		case 8:
			printf("B");
			break;
		case 7:
			printf("C");
			break;
		case 6:
			printf("D");
			break;
		default:
			printf("E");
			break;
	}
	return 0;
}