#include <iostream>
#include <iomanip>
#include <fstream>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <vector>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <algorithm>
#include <sstream>
#include <fstream>
using namespace std;

int N;

int Zero(int N) {
    int P = 5, Nr = 0;
    while (N >= P) {
        Nr += N / P;
        P *= 5;
    }
    return Nr;
}

int Solution(int X) {
    int L = 1, R = 1000000000, M;
    while (R - L > 1) {
        M = (L + R) / 2;
        if (Zero(M) < X) L = M; else R = M;
    }
    return Zero(L) == X ? L : Zero(R) == X ? R : -1;
}

int main(){
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);

    cin >> N;
    cout << Solution(N);

    return 0;
}