#include<iostream>
#include<fstream>

using namespace std;

int main()
{

	int n;
	int suma = 1;
	int fact = 0;

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

	f >> n;

	if (n == 0)
	{
		g << "-1";
		return 0;
	}

	while (n != 0)
	{
		if (suma % 10 == 0)
		{
			n--;
			suma = suma / 10;
		}
		suma =suma * (fact+1);
		fact ++;
	}

	g << fact-1;

	f.close();
	g.close();

}