Дан двумерный массив. Необходимо элементы строк заменить нулями кроме строки S- Pascal(Паскаль)

Program mas;

Uses crt;

Const
  m = 5;
  n = 4;

Var
  a: array [1 .. m, 1 .. n] of byte;
  i, j, s: byte;

Begin
  Writeln('Vvedite s ще 1 do 5');
  readln(s);
  For i := 1 to m do
  begin
    For j := 1 to n do
    begin
      a[i, j] := random(21);
      Write(a[i, j]:4);
    end;
    Writeln();
  end;
  for i := 1 to m do
    for j := 1 to n do
      if i <> s then
        a[i, j] := 0;
  Writeln('---------------');
  For i := 1 to m do
  begin
    For j := 1 to n do
    begin
      Write(a[i, j]:4);
    end;
    Writeln();
  end;

End.