#include <iostream>
#include <fstream>

using namespace std;

int main ()
{
	ifstream in ("fact.in");
	ofstream out ("fact.out");

	long p;
	int i = 1;
	int c = 0;
	int a;

	in >> p;

	if (p == 0)
	{
		out << 1 << endl;
		return 0;
	}
	
	while (c < p)
	{
		a = i;
		while (a % 5 == 0)
		{
			c++;
			a /= 5;
		}

		i++;
	}

	out << i - 1;

	return 0;
}