# include<fstream>
using namespace std;
int nr_zerouri(int n)
{
    int p;
    p=0;
    while (n>0)
    {
        p=p+n/5;
        n=n/5;
    }
    return p;
}
int main()
{
    ifstream cin("fact.in");
    ofstream cout("fact.out");
    int p,i,x,nr,n;
    cin >> p;
    x=0; n=1;
    while(x<p)
    {
      n++;
      x=nr_zerouri(n);
    }
    if(x==p)
    {
        cout << n;
    }
    else
    {
        cout << "-1" ;
    }
}