#include <stdio.h>

int main() {
    int input;
    scanf("%i", &input);
    printf("Your input was: %i\n", input);

    if ((input >= 0) && (input <= 100)) {
        char letter;
        int inputRange = input/10;

        switch(inputRange) {
            case 10:
            case 9:
                letter = 'A';
                break;
            case 8:
                letter = 'B';
                break;
            case 7:
                letter = 'C';
                break;
            case 6:
                letter = 'D';
                break;
            case 5:
            default:
                letter = 'F';
        }

        printf("Your letter grade is %c\n", letter);
    } else {
        printf("ERROR: Input must be no more than 100 and no less than 0\n");
        return 1;
    }

    return 0;
}