var n,p,k,i:longint;
    f:text;

function nr5(k:longint):longint;
var kont:longint;
begin
  kont:=0;
  while k mod 5=0 do
    begin
      k:=k div 5;
      inc(kont);
    end;
  nr5:=kont;
end;

begin
  assign(f,'fact.in');
  reset(f);
  read(f,p);
  close(f);
  assign(f,'fact.out');
  rewrite(f);
  if p=1 then
    write(f,5)
  else if p<1 then write(f,-1)
  else
    begin
      k:=1; n:=5; i:=1;
      while i<p do
        begin
          inc(k); inc(n,5);
          inc(i,1+nr5(k));
        end;
      write(f,n);
    end;
  close(f);
end.