#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int nz(int n)
{
    int s=0,p=5;
    while(p<=n)
    {
        s=s+n/p;
        p=p*5;
    }

    return s;
}
int main()
{
    int c=1,p;
    fin>>p;
    if(p==0)
    {
        cout<<1;
    }
    else
    {
        while(nz(5*c)<=p)
        {
            c++;
        }

        if(nz(5*(c-1))==p)
        {
            fout<<5*(c-1);
        }
        else
            fout<<-1;
    }


    return 0;
}