#include <stdio.h>

main()
{
int score;
char ans, buf[80];

do {
printf("Input a score: "); scanf("%d", &score);
if( score >= 90) {
printf("A\n");
} else if (score >= 80) {
printf("B\n");
} else if (score >= 70) {
printf("C\n");
} else if (score >= 60) {
printf("D\n");
} else {
printf("F\n");
}
gets(buf);
printf("Input another score (y/n)? ");
scanf("%c", &ans);
} while (toupper(ans) == 'Y');
return 0;
}