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

int main(void)
{
    char* buffer1;
    buffer1 = calloc(1, 14);
    if (!buffer1) { fprintf(stderr, "Memory Failure.\n"); exit(EXIT_FAILURE); }

    int a = 15;
    int b = 25;
    char c[4] = "MON";

    int k = snprintf(buffer1, 13, "%02d%02d%s", a, b, c);
    printf("k is %d; buffer1 has [%s]\n", k, buffer1);
    free(buffer1);

    return 0;
}