#include <iostream>
#include <fstream>

using namespace std;

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

int num_zero(long long x) {
	int zero = 0;
	while (x % 10 == 0)
		x /= 10,zero++;
	return zero;
}

int main()
{
	int p, n=1, i = 2;
	in >> p;
	while (num_zero(n) != p) {
		n *= i;
		i++;
	}
	out << i;

	in.close();
	out.close();
}