#include <fstream>
using namespace std;
int main ()
{
	ifstream fin ("fact.in");
	ofstream fout ("fact.out");
	long n,p,x,k=0;
	fin>>p;
	if (p==0) {fout<<"1"; return 0;}
	for (n=5;k<p;n+=5)
		{x=n;
		 while (x%5==0){k+=x/5;x=x/5;}
		}
	n=n-5;
	if (k==p) fout<<n;
		else fout<<"-1";
	return 0;
}