#include "pch.h"
#include <iostream>

#include <fstream> 

ifstream f("fact.in");
ofstream g("fact.out");
 
int n;
long long r, pas;

int zero(int x) {
	int ans = 0;
	while (x >= 5) {
		ans += x / 5;
		x = x / 5;
	}
	return ans;
}


using namespace std;
int main()
{  
	f >> n;
	pas = 1 << 30;
	r = 0;
	while (pas) {
		if (zero(r + pas) < n) r += pas;
		pas /= 2;
	}
	if (zero(r + 1) == n) {
		g << r + 1 << '\n';
	}
	else {
		g << -1;
	}
	return 0;
}