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

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

int number_of_zeros(int n) {
	
	int s = 0;
	int a = 5;
	// numarul de zerouri este egal cu numar factorilor divizibili cu 5
	while(a <= n) {
		s += n/a;
		a *= 5;
	}
	
	// s - numar zerouri
	
	return s;	
}

int main() {

	int p, left, right, ans;
    in >> p;
	left = 1; 
	right = 100000000;
	while(left <= right) {
		int mid = left + (right-left)/2;
		if(number_of_zeros(mid) >= p) {
			ans = mid;
			right = mid - 1;
		}
		else {
			left = mid + 1;
		}
		//debug() << imie(left) imie(mid) imie(right);
	}
		if(number_of_zeros(ans) == p) {
			out << ans;
		}
		else {
			out << -1;
		}
	
	return 0;
}

//2 -> 10! pentru ca 10! are 2 zerouri la final