Дана задача отсортировать массив по убыванию методом выбора максимального элемента — Pascal(Паскаль)

program dark_side;

uses crt;

type
  ar = array [1 .. 100] of integer;

var
  i, n, f, j, t, i_max: integer;
  a: ar;

begin
  clrscr;
  randomize;
  writeln('enter length');
  readln(n);
  writeln('1.Input by hand');
  writeln('2.Autofill');
  read(f);
  if f = 1 then
    for i := 1 to n do
    begin
      write('a[', i, ']=');
      readln(a[i]);
    end
  else
    for i := 1 to n do
      a[i] := random(100);
  for i := 1 to n do
    write(a[i]:3);
  writeln;
  for i := 1 to n - 1 do
  begin
    i_max := i;
    for j := i_max + 1 to n do
      if a[j] > a[i_max] then
        i_max := j;
    t := a[i];
    a[i] := a[i_max];
    a[i_max] := t;
  end;
  readln;
  for i := 1 to n do
    write(a[i]:3);
  readln;

end.