// Cuenta cuántas veces aparece cada nota, de 0 a 20, y escribe las que aparecen.
#include <stdio.h>
#include <stdlib.h>

#define MAX_GRADE 20

int main(void) {
    const int grades[] = {14, 20, 7, 14, 20, 11};
    int total = sizeof(grades) / sizeof(grades[0]);

    int *counts = calloc(MAX_GRADE, sizeof *counts);
    if (counts == NULL) {
        return 1;
    }

    for (int i = 0; i < total; i++) {
        counts[grades[i]]++;
    }

    for (int grade = 0; grade <= MAX_GRADE; grade++) {
        if (counts[grade] > 0) {
            printf("%d: %d\n", grade, counts[grade]);
        }
    }

    free(counts);
    return 0;
}