procedure SPLINT(XA, YA, Y2A:array of real; N:integer; X:real;var Y:real);
label 1;
var
    K,KLO,KHI:integer;
    H,A,B,AAA,BBB,Q,QQ:real;
begin
    KLO:=1;
    KHI:=N;
1:  If KHI - KLO > 1 Then
    begin
        K:=(KHI + KLO) Div 2;
        If XA[K] > X Then
            KHI:=K
        Else
            KLO:=K;
        GoTo 1;
    end;
    H:=XA[KHI] - XA[KLO];
    If H = 0 Then
    begin
        ShowMessage('  PAUSE  "BAD  XA  INPUT"');
        Exit;
    end;
    A:=(XA[KHI] - X) / H;
    B:=(X - XA[KLO]) / H;
    AAA:=A * YA[KLO] + B * YA[KHI];
    if A = 0 then
      Q:= 0
    else
      if A > 0 then
        Q:= exp(3*ln(A))
      else
        Q:= -EXP(3*LN(-A));
    if B = 0 then
      QQ:= 0
    else
      if B > 0 then
        QQ:= exp(3*ln(B))
      else
        QQ:= -EXP(3*LN(-B));
    BBB:=(Q - A) * Y2A[KLO] + (QQ - B) * Y2A[KHI];
    Y:=AAA + BBB * (H * H) / 6;
end;