var p,k,i:longint;
    n:qword;
    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,0)
  else
    begin
      n:=0; i:=0;
      while i<p do
        begin
          k:=1;
          while (i<p) and (k<=4) do begin inc(n,5); inc(i); inc(k); end;
          if i<p then begin inc(n,5); inc(i,nr5(n)); end;
        end;
      if i=p then write(f,n)
             else write(f,-1);


    end;
  close(f);
end.