procedure LUBKSB(var A:matrx2; N:integer; var INDX,B:array of real);
var
    I,LL,J,II:integer;
    SUM:real;
BEGIN
    II:=0;
    For I:=1 To N DO
    begin
        LL:=Trunc(INDX[I]);
        Sum:=B[LL];
        B[LL]:=B[I];
        If II <> 0 Then
        begin
            For J:=II To I - 1 do
                Sum:=Sum - A[I, J] * B[J];
        end
        Else If Sum <> 0 Then
            II:=I;
        B[I]:=Sum;
    end;
    For I:=N DownTo 1 do
    begin
        Sum:=B[I];
        If I < N Then
        begin
            For J:=I + 1 To N do
                Sum:=Sum - A[I, J] * B[J];
        end;
        B[I]:=Sum / A[I, I];
    end;
End;