#include <iostream>
#include<fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
long n,cn,p,p5;
int main()
{f>>p;
if (p==0)
      g<<1;
else{n=0;
      while(p5<p)
      {
            n=n+5;
            cn=n;
            while(cn%5==0)
                  {
                        p5++;
                        cn=cn/5;
                  }
      }
      if(p5>p)
            g<<-1;
      else  g<<n;
}
    return 0;
}