var n,q,z,f:int64;
begin
  assign(input,'fact.in'); reset(input);
  assign(output,'fact.out'); rewrite(output);
  readln(q);
  if q=0 then write(1)
  else begin
    n:=4*q; n:=n-n mod 5;
  end;
  f:=5; while (f<=n) do begin z:=z+n div f; f:=f*5; end;
  repeat
    if z<q then n:=n+5;
    f:=n; while f mod 5=0 do begin inc(z); f:=f div 5; end;
  until z>=q;
  if z=q then write(n)
  else write(-1);
close(input); close(output);
end.