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

int main()
{
	ifstream fin("fact.in");
	ofstream fout("fact.out");
	int p, n = 1, cp, cn, k, np = 0, nn = 0;
	fin >> p;

	for (int i = 1; i <= p; i++)
		n *= i;

	k = n;
	while (k != 0)
	{
		cn = k % 10;
		nn++;
		k /= 10;
	}
	while (p != 0)
	{
		cp = k % 10;
		np++;
		p /= 10;
	}

	if (nn == np) fout << n;
	else fout << -1;

	system("pause");
	return 0;
}