#include <bits/stdc++.h>

using namespace std;

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

int countzero(int n) {
    int p5, d5;

    if(n == 0) {
        return 0;
    }

    d5 = 0;
    p5 = 5;
    while(p5 <= n) {
        d5 += n / p5;
        p5 *= 5;
    }

    return d5;
 }

int main()
{
    int p, st, dr, mid;
    fin >> p;
    st = 0;
    dr = 1000000000;
    while(dr - st > 1) {
        mid = (st + dr) / 2;
        if(countzero(mid) >= p) {
            dr = mid;
        }else{
            st = mid;
        }
    }


    if(countzero(st) == p) {
        fout << st + (st == 0) << "\n";
    }else if(countzero(dr) == p) {
        fout << dr + (dr == 0) << "\n";
    }else{
        fout << "-1\n";
    }


    return 0;
}