Pascal: sum of array cells behind maximum index

{ ... find the sum of all elements behind (after) first maximum element. Display a message if there are none. }
const n = 6;
var m: array[1 .. n] of Integer;
    i, mxIndex, mxValue, sum: Integer;
begin
    { input }
    for i := 1 to n do begin
        write('M[', i, '] = ');
        readLn(M[i]);
    end;
    { find max }
    mxIndex := 0;
    mxValue := 0;
    for i := 1 to n do begin
        if (mxIndex = 0) or (M[i] > mxValue) then begin
            mxIndex := i;
            mxValue := M[i];
        end;
    end;
    { sum-related }
    if (mxIndex < n) then begin
        sum := 0;
        for i := mxIndex + 1 to n do sum := sum + M[i];
        writeLn('Sum: ', sum);
    end else writeLn('There are no elements behind the maximum');
end.