#include<fstream.h>
#include<iostream.h>
int main(void)
{
  fstream f,g;
  long int x=1,p,temp=0,i;
  f.open("fact.in",ios::in);
  f>>p;
  f.close();
  while(x<p)
    x=x*5+1;
  x=(x-1)/5;
  g.open("fact.out",ios::out);
  if(p==0)
    g<<1;
  else
  {
    if(p%x==5)
      g<<-1;
    else
    {
      for(i=6;i<=x;i=i*5+1)
	temp=temp+p/i;
      g<<(p-temp)*5;
    }
  }
  return 0;
}