#include <stdio.h>

int main ()
{
	double p, k;
	double n;
	freopen("fact.in", "r", stdin);
	freopen("fact.out", "w", stdout);
	scanf("%lf", &p);

	k=1;
	do
	{
		k*=5;
		n=4.*k/(k-1.)*(p+1);
	}
	while((long)n/k>5);

	if(n)
		printf("%ld", (long)n-(long)n%5);
	else
		printf("-1");
	
	return 0;
}