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

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

int p;

int main()
{
	fin >> p;
	int i = 2, ct2 = 0, ct5 = 0;
	while (ct2 < p || ct5 < p)
	{
		int aux = i;
		while (aux % 2 == 0)
		{
			ct2++;
			aux /= 2;
		}
		while (aux % 5 == 0)
		{
			ct5++;
			aux /= 5;
		}
		i++;
	}
	fout << i - 1;
	return 0;
}