const SIZE = 100; var n...

const
  SIZE = 100;
var
  n, m, p, count, ans, x, y, i, j : integer;
  a : array[1..SIZE, 1..SIZE] of integer;
procedure colour(x, y : integer);
begin
  inc(count);
  a[x][y] := 1;
  if (x > 1) and (a[x - 1][y] = 0) then colour(x - 1, y);
  if (y > 1) and (a[x][y - 1] = 0) then
    colour(x, y - 1);
  if (x < n) and (a[x + 1][y] = 0) then colour(x + 1, y);
  if (y < m) and (a[x][y + 1] = 0) then
    colour(x, y + 1);
end;
begin
  fillchar(a, sizeof(a), 0);
  readln(n, m, p);
  for i := 1 to p do
  begin
    read(x, y);
    a[x][y] := 1;
  end;
  ans := 0;
  for i := 1 to n do
    for j := 1 to m do
      if a[i][j] = 0 then
      begin
        count := 0;
        colour(i, j);
        if (ans < count) then ans := count;
      end;
  writeln(ans);
end.