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

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

int numOf5(int a)
{
	int b = 0;
	while (a % 5 == 0 && a != 0)
	{
		b++;
		a /= 5;
	}
	return b;
}
int biggest(int a)
{
	int s = 5;
	while (s < a)
	{
		s *= 5;
	}
	return s / 5;
}
int main()
{
	int n,p = 0, s = 25;
	f >> n;
	if (n == 0)
	{
		g << 1;
		return 0;
	}
	/*while (p < n)
	{
		p += numOf5(s / 5) + 5;
		s += 25;
	}
	s -= 25;
	*/
	p = n;
	s = n * 5;
	int s1 = s;
	int b = biggest(s);
	while (b % 25 == 0)
	{
		p += s / b;
		b /= 5;
	}
	while (p > n)
	{
		p -= numOf5(s / 5) + 1;
		s -= 5;
	}
	if (p == n)
		g << s;
	else
		g << -1;
	return 0;
}