#include <iostream>
#include <fstream>
#include <climits>

using namespace std;

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

long long nr_zero(long long nr)
{
    long long nrz=0,i;
    cout<<5LL<<"   ";
    for(i=5;i<=nr;i*=5)
    {
        nrz+=nr/i;
    }
    return nrz;
}

int main()
{
    long long n=0,rez=0,ls=1,ld=LONG_MAX;
    fin>>n;
    while(ls<=ld)
    {
        long long m = ls + (ld-ls)/2;
        if(nr_zero(m) == n)
        {
            ld = m-1;
            rez = m;
        }
        else
        {
            if(n<nr_zero(m))
            {
                ld=m-1;
            }
            else
            {
                ls = m+1;
            }
        }
    }
    if(rez == 0)
        fout<<-1;
    else
        fout<<rez;
    return 0;
}