#include <iostream>
#include <fstream>
using namespace std;
int p,nr,x;
int main()
{
    ifstream f("fact.in");
    ofstream g("fact.out");
    f>>p;
    cin>>p;
    while(nr<p)
    {nr=nr+1;
    while(nr%5==0)
    {
        x=x+1;
    }
    nr=nr+x;
    }
    if (nr==p) nr<<nr*5;
    else nr<<-1;
    g<<nr;

}