#include <stdio.h>

int main()
{
    int p, n, coef;

    FILE *fin = freopen("factorial.in", "r", stdin);
    FILE *fout = freopen("factorial.out", "w", stdout);

    scanf("%d", &p);

    coef = (p-1);
    n = p * 5;

    while(coef)
    {
        if(coef % 5 == 0)
        {
            printf("-1\n");
            return 0;
        }
        coef /=  5;
        n -= 5 * coef;

    }

    printf("%d\n", n);

}