procedure getprime;
var
  i, j: Longint;
  p: array[1..50000] of Boolean;
begin
  FillChar(p, SizeOf(p), true);
  p[1] := false;
  i := 2;
  while i < 50000 do
  begin
    if p[i] then
    begin
      j := i * 2;
      while j < 50000 do
      begin
        p[j] := false;
        Inc(j, i);
      end;
    end;
    Inc(i);
  end;
  l := 0;
  for i := 1 to 50000 do
    if p[i] then
    begin
      Inc(l);
      pr[l] := i;
    end;
end;

function prime(x: Longint): Integer;
var
  i: Integer;
begin
  prime := false;
  for i := 1 to l do
    if pr[i] >= x then
      Break
  else if x mod pr[i] = 0 then
    Exit;
  prime := true;
end;
//delphi/6603