procedure QSIMP(A, B:real; var S:real);
const
    EPS = 0.000001;    JMAX = 20;
var
    J:integer;  OST,OS,ST:real;
begin
    OST:=-1E+30;
    OS:=-1E+30;
    For J:=1 To JMAX do
    begin
        TRAPZD(A, B, ST, J);
        S:=(4 * ST - OST) / 3;
        If Abs(S - OS) < EPS * Abs(OS) Then Exit;
        OS:=S;
        OST:=ST;
    end;
    ShowMessage('Too many steps.');
end;