#include<iostream>
#include<fstream>
using namespace std;

int main()
{
	int P,c,n;
	ifstream f("factorial.in");
	ofstream g("factorial.out");
	f>>P;
    n=1;
	while(P>0)
	{
		n++;
		if(n%5==0)
		{
			c=n;
			while(c%5==0)
			{
				P--;
				if(P < 0) {
					g << -1;
					f.close();
					g.close();
					return 0;
				}
				c=c/5;
			}
		}
	}
	g<<n;
	f.close();
	g.close();
	return 0;
}