Q568: Just the Facts

// Run time: 0.010
#include <stdio.h>

int main()
{
    int n;
    int i;
    long long int prod;
    while (scanf("%d", &n) != EOF)
    {
        prod = 1;
        for ( i = 2; i <= n; i++)
        {
            prod *= i;
            while (!(prod%10))  prod /= 10;
                prod %= 100000;
        }
        printf("%5d -> %lld\n", n, prod%10);
    }

    return 0;

}