#include <stdio.h>

long p,a = 1,b = 100000000,gasit;

long zerouri (int x)
{
	long put = 0;
	while (x > 0)
		{
			put += x / 5;
			x /= 5;
		}
	return put;
}

int main ()
 {
	long aux;
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	scanf("%ld",&p);
	while (a != b && !gasit)
	{
		aux = zerouri((a+b)/2);
		if (aux == p)
			gasit = 1;
		else
			if (aux < p)
				a = (a+b)/2 +1;
			else
				b = (a+b)/2;
	}
	
	if (gasit)
		{
			long y = (a+b)/2;
			while (y%5)
				--y;
			printf("%ld",y);
		}
	else
		printf("-1");
	
	return 0;
 }