#include <stdio.h>

enum months {
    JAN = 1, FEB, MAR, APR, MAY, JUN, JUL, AUG, SEP, OCT, NOV, DEC
};

const int month_days[12 + 1] = {
    0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
};

int main(void)
{
    enum months month;
    int i, j;
    int matrix[3][5] = { { 1,  2,  3,  4,  5},
                         { 6,  7,  8,  9, 10},
                         {11, 12, 13, 14, 15} };

    /* Vector */
    month = DEC;
    printf("%d días\n", month_days[month]);

    /* Array */
    for (i = 0; i < 3; i++) {
        for (j = 0; j < 5; j++) {
            printf("%2d ", matrix[i][j]);
        }
        printf("\n");
    }

    return 0;
}