C＃ 仲良し Delphi Round 2

program Project1;
{$APPTYPE CONSOLE}
uses SysUtils, Windows;
function calc(x1, y1, x2, y2: Real; Depth: Integer): Real;
var
x, y: Real;
begin
if x1 * x1 + y1 * y1 >= 1 then
Result := 0
else if x2 * x2 + y2 * y2 <= 1 then
Result := (x2-x1)*(y2-y1)
else if Depth <= 0 then
Result := (x2-x1)*(y2-y1) / 2
else
begin
x := (x1 + x2) / 2;
y := (y1 + y2) / 2;
Result := calc(x1, y1, x , y , Depth-1) + calc(x1, y , x , y2, Depth-1) + calc(x , y1, x2, y , Depth-1) + calc(x , y , x2, y2, Depth-1) ;
end;
end;
function getpi: Real;
begin
Result := calc(0,0,1,1,27) * 4;
end;
var
ct: Cardinal; pi: Real;
begin
ct := GetTickCount;
pi := getpi;
Writeln('pi=', pi, ' time=', GetTickCount-ct, 'ms');
end.