#include <stdio.h>

int main() {
	int x;
	scanf("%d",&x);
	if (  x>=90    )
		printf("S  \n");
	else if (     x>=80  )
		printf("  A\n");
	else if (  x>=60     )
		printf(" B \n");
	else
		printf(" C \n");
	return 0;
}