#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");

long long catidezero(long long P)
{
    long long i=5,contor=0;
    while (i<=P)
    {
       contor+=(P/i);
       i*=5;
    }
    return contor;
}

int main()
{
    long long P,cP;
    fin >> P;
    if (P==0)
    {
        cP=1;
        fout << cP;
    }
    else
    {
        cP=P;
        while (catidezero(cP)<P)
        {
            ++cP;
        }
        if (catidezero(cP)==P)
        {
            fout << cP;
        }
        else
        {
            cP=-1;
            fout << cP;
        }
    }
    return 0;
}