#include<fstream.h>
ifstream intrare("fact.in");
ofstream iesire("fact.out");
long p;
long verif(long long c)
{
		long i=0;
		while((c!=0)&&(i<=p+5))
		{
			i+=c/5;
			c/=5;
		}
		return i;
}
void cautbin(long long a,long long b)
{
	if(a<b)
	{
	long long c=(a+b)/2;
	long x=verif(c);
	if(x>p) cautbin(a,c-1);
	else if(x<p) cautbin(c+1,b);
	else iesire<<c-(c%5);
	}
	else iesire<<"-1";
}
int main()
{
	intrare>>p;
	cautbin(0,1000000000);
	return 0;
}