h, w = read_line.split.map(&.to_i)
a = Array.new(h) { read_line.split.map(&.to_i) }
ans = 0
(h - 1).times do |y|
  ps = w.times.select { |i| a[y][i] == 1 }.to_a
  0.step(to: ps.size - 2, by: 2) do |i|
    a[y + 1][ps[i]] ^= 1
    a[y + 1][ps[i + 1]] ^= 1
  end
  ans += ps.size % 2
end
last = a[h - 1].sum
if last >= 2 && ans > 0
  puts ans + last - 2
else
  puts ans + last
end