#include <bits/stdc++.h>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int f(int x){
	int t=x;
	while(x){
		x /= 5;
		t+=x;
	}
	return t;
}
int main() {
	int x;
	fin>>x;
	if(x == 0){
		fout << 1;
		return 0;
	}
	int lt=1;
	int mid, y;
	int right = x;
	while(lt<=right){
		mid = lt+(right-lt)/2;
		y=f(mid);
		if(y==x) {
			lt = mid;
			break;
		}
		if(y<x){
			lt = mid + 1;
		} else {
			right = mid - 1;
		}
	}
	if(f(lt) == x){
		fout << lt*5;
	} else {
		fout << -1;
	}
	return 0;
}