#include <iostream>
#include <fstream>
#include <cmath>
#define NMax 1000000000
using namespace std;
ifstream f("cmmdc.in");
ofstream g("cmmdc.out");

int fact(int x)
{
  int nr=0,p=5;
    while (x>=p)
    {
        nr+=x/p;
        p*=5;
    }
    return nr;
}

int main ()
{
    int p,val;
    f >> p;
    if (p==0) g <<1;
    else
    {
        int min=1,max=NMax,mid;
        bool ok=false;
        while (min<=max && !ok)
        {
            mid=(min+max)/2;
            val=fact(mid);
            if (val<p) min=mid+1;
            else if (val>p) max=mid-1;
            else ok=true;
        }
    if (ok)
        {
       while (mid%5) mid--;
            g <<mid;
        }
        else g <<-1;
    }
}