#include <bits/stdc++.h>
#define mod 20011

using namespace std;

ifstream fin("fact.in");
ofstream fout("fact.out");
int p, st, dr, m, z;

static inline int zero(int nr) {
    int nm = 0;
    while(nr >= 5) {
        nr /= 5;
        nm += nr;
    }
    return nm;
}

int main() {
    fin >> p;
    st = 1;
    dr = p * 5;
    while(st < dr) {
        m = st + (dr - st) / 2;
        if(zero(m) < p) st = m + 1;
        else dr = m - 1;
    }
    if(zero(st) == p) fout << st;
    else fout << "-1";

    return 0;
}