#include <fstream>
#include <climits>
using namespace std;

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

unsigned nrzero(unsigned x){
    unsigned nr = 0, t = 5;
    while (x / t > 0){
        nr += x / t;
        t *= 5;
    }
    return nr;
}

int main(){
    unsigned P, st, dr, mij;
    fin >> P;
    if (P == 0)
        fout << 1 << '\n';
    else{
        st = 0;
        dr = UINT_MAX / 5 + 1;
        while (dr - st > 1){
            mij = (dr + st) / 2;
            if (nrzero(5 * mij) <= P)
                st = mij;
            else
                dr = mij;
        }
    if (nrzero(5 * st) != P)
        fout << -1 << '\n';
    else
        fout << 5 * st << '\n';
    }
    fin.close();
    fout.close();
    return 0;
}