procedure POLINT(XA, YA:array of real; N:integer; X:real; var Y, DY:real);
var
    C,D:array[0..10] of real;
    DIF,DIFT,HO,HP,W,DEN:real;
    NS,I,M:integer;
begin
    NS:=1;
    DIF:=Abs(X - XA[1]);
    For I:=1 To N do
    begin
        DIFT:=Abs(X - XA[I]);
        If DIFT < DIF Then
        begin
            NS:=I;
            DIF:=DIFT;
        end;
        C[I]:=YA[I];
        D[I]:=YA[I];
    end;
    Y:=YA[NS];
    NS:=NS - 1;
    For M:=1 To N - 1 do
    begin
        For I:=1 To N - M do
        begin
            HO:=XA[I] - X;
            HP:=XA[I + M] - X;
            W:=C[I + 1] - D[I];
            DEN:=HO - HP;
            If DEN = 0 Then
            begin
                ShowMessage('PAUSE');
                Exit;
            end;
            DEN:=W / DEN;
            D[I]:=HP * DEN;
            C[I]:=HO * DEN;
        end;
        If 2 * NS < N - M Then
            DY:=C[NS + 1]
        Else
        begin
            DY:=D[NS];
            NS:=NS - 1;
        end;
        Y:=Y + DY;
    end;
end;