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

unsigned long reverse(unsigned long n) {
    unsigned long r = 0;
    while (n > 0) {
        r += n % 10;
        r *= 10;
        n /= 10;
    }
    r /= 10;
    return r;
}

int main(int argc, char **argv) {
    if (argc != 2) {
        printf("Usage: %s number\n", argv[0]);
        return 1;
    }

    unsigned long n = strtoul(argv[1], NULL, 0);
    unsigned long r = reverse(n);
    printf("%lu reversed is %lu.\n", n, r);

    return 0;
}