#include <bits/stdc++.h>
#include <math.h>
#define ll long long int
#include <fstream>

using namespace std;

ifstream f("fact.in");
ofstream g("fact.out");

int zero(ll n)
{
    ll nrz=0;
    for(int i = 5;i<=n;i*=5)
        nrz += n/i;

    return nrz;
}


int main()
{

    ll p;
    f>>p;

    ll m,s=1,d=1000000000;

    while(s<=d)
    {
        m = (s+d)/2;

        if(zero(m) < p)
            s = m+1;
        else
            d = m-1;
    }


    if(zero(s) == p)
        g<<s;
    else
        g<<"-1";

    return 0;
}