#include<iostream>
#include<math.h>
#include<fstream>

using namespace std;

ifstream f;
ofstream g;

unsigned long p,n,i;

void citire()
{
    f.open("fact.in");
    f >> p;
    f.close();
}

void scriere()
{
    g.open("fact.out");
    g << n;
    g.close();
}

int main()
{
    citire();

    if(p==0)
        n=1;
    for(i=0;i<=11;i++)
    {
        if(p>pow(5,i)&&p<pow(5,i+1))
            n=(p-i)*5;
        if(p==pow(5,i)+i-1)
            n=-1;
    }


    scriere();

    return 0;
}