procedure LOCATE(XX:array of real; N:integer; X:real; var J:integer);
label 10;
var
    JL,JU,JM:INTEGER;
begin
    JL:=0;
    JU:=N + 1;
10: If JU - JL > 1 Then
    begin
        JM:=(JU + JL) Div 2;
        If (XX[N] > XX[1]) = (X > XX[JM]) Then
            JL:=JM
        Else
            JU:=JM;
        GoTo 10;
    end;
    J:=JL;
end;