#include <iostream>
#include <fstream>
#define ll long long
using namespace std;

string nume = "fact";
///string nume = "aplicatie";

ifstream f(nume + ".in");
ofstream g(nume + ".out");

ll n, p, st = 1, dr = 500000000, m;

ll NrZerouri(ll nr)
{
	ll cnt = 0, factor = 5;
	while (factor <= nr)
		cnt += (nr / factor), factor *= 5;
	return cnt;
}

int main()
{
	f >> n;

	while (st <= dr)
	{
		m = (st + dr) / 2;
		if (NrZerouri(m) >= n)
			dr = m - 1, p = m;
		else
			st = m + 1;
	}

	if (NrZerouri(p) == n)
		g << p;
	else g << -1;

	f.close();
	g.close();
    return 0;
}