#include<bits/stdc++.h>

#define ll long long
#define pii pair<int,int>
#define pll pair<ll,ll>
#define fi first
#define se second
#define sz size
#define pb push_back
#define mp make_pair
#define bg begin
#define nd end
using namespace std;

#define int long long

const int maxn = 100003;
const int maxk = 1003;

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

int nrZero(int x){
 
    int ret =0 ;
    while(x){
        ret+=x/5;
        x/=5;
    }
    return ret;
}


int32_t main(){

	// #ifndef ONLINE_JUDGE
	// freopen("input.in","r",stdin);
	// #endif

	ios_base::sync_with_stdio(false);

	int p;

	fin >> p;

	int lo = 0,hi = (int)(1e9);

	if(p == 0){
		fout << 1 << '\n';
		return 0;
	}

	while(hi - lo > 1){

		int mid = (lo + hi) >> 1;
		if(nrZero(mid) >= p){
			hi = mid;
		}
		else{
			lo = mid;
		}
	}
	if(nrZero(lo) != p && nrZero(hi)!=p){
		fout << -1 << '\n';
		return 0;
	}
	if(nrZero(lo) == p){
		fout << lo << '\n';
	}
	fout << hi << '\n';

	return 0;
}