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

ifstream fi ("fact.in");
ofstream fo ("fact.out");
long long p, s;

int putere(long long a)
{
    s = 0;
    long long ca = a;
    while (ca)
    {
        s+=ca/5;
        ca/=5;
    }
    return s;
}

void binar()
{
    long long hi = 5*p, lo = 1, mid;
    while (hi > lo)
    {
        mid = (hi + lo)/2;
        if (putere(mid) < p)
            lo = mid + 1;
        else
            hi = mid;
    }
    if (putere(hi) != p)
        fo << -1;
    else
        fo << hi;
}

int main ()
{
    fi >> p;
    binar();
    return 0;
}