#include <stdio.h>
#include <stdlib.h>

int main() {
    printf("Please enter a whole number percentage (0-100): ");
    char inputText[4];
    fgets(inputText, 4, stdin);
    printf("inputText: %s\n", inputText);
    long int input;
    input = strtol(inputText, NULL, 0);
    printf("input: %li\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);
        return 0;
    } else {
        printf("ERROR: Input must be no more than 100 and no less than 0\n");
        return 1;
    }
}