#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>

typedef long long ll;

const ll mod=1e9+7;
const ll inf=-2e18;

const int dx[] = {0, 1, 0, -1};
const int dy[] = {1, 0, -1, 0};

#define all(x) x.begin(),x.end()
#define allr(x) x.rbegin(),x.rend()
#define rc(x)  return cout<<x<<"\n",0
#define sz(s)  (int) s.size()
#define pb push_back
#define mp make_pair
#define fr first
#define sc second
#define PI 3.14159265358979

using namespace std;

ll t,x;

int nr5(int p) {
	ll c=5;
	ll nr=0;
	while (p/c!=0) {
		nr+=p/c; c*=5;
	}
	return nr;
}

// Pentru nr factoriale, pentru fiecare i*5 numere apare un 0, unde i face parte din multimea nr naturale 
// (fiecare 5 nr, fiecare 25 nr, fiecare 150 nr etc)

int main() {
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	ifstream cin("fact.in");
	ofstream cout("fact.out");
	cin >> x;
	ll l=1,r=1e8;
	ll mid,ans=-inf;
	// caut binar valoarea care are un nr p de 0-uri in baza formulei de mai sus
	while (l<=r) {
		mid=l+(r-l)/2;
		ll nr_consc=nr5(mid);	
		if (nr_consc==x) {
			ans=mid;
			r=mid-1;
		}
		else {
			if (nr_consc>x) {
				r=mid-1;
			}
			else {
				l=mid+1;
			}
			
		}
		
	}
	if (ans==-inf)cout << "-1\n";
	else cout << ans << '\n';
}