#include <iostream>
#include <fstream>

using namespace std;

int main () {

ifstream in ("fact.in");
ofstream out ("fact.out");

int n, i, count, den;

in >> n;
for (i = n; count >= n; i--)
{
	den = 5;
	count = 0;
	while (i * 5  >= den)
	{
		count += (i*5) / den;
		den *= 5;
	}
	if (count == n)
	{
		out << i * 5;
		break;
	}
}
if (count != n)
	out << -1;
			

return 0;
}