#include <stdio.h>

int sum = 0, rem;
int reverse(int num)
{
    if (num)
    {
        rem = num % 10;
        sum = sum * 10 + rem;
        reverse(num / 10);
    }
    return sum;
}

void main()
{
    int num = 54321;
    printf("New num is: %d\n",reverse(num));
}