#!/usr/bin/python2
# -*- coding: utf-8 -*-
# †
from itertools import chain
flatten = chain.from_iterable

R, C = map(int, raw_input().split())
board_width  = C
board_height = R
n = board_width * board_height

# Set up the matrix of button pushes
A = [[0]*n for i in xrange(n)]
for i in xrange(board_width):
  for j in xrange(board_height):
    idx = i + j * board_width
    A[idx][idx] = 1
    if i > 0:                A[idx - 1][idx] = 1
    if i < board_width - 1:  A[idx + 1][idx] = 1
    if j > 0:                A[idx - board_width][idx] = 1
    if j < board_height - 1: A[idx + board_width][idx] = 1
    #
    if i > 0 and j > 0:                A[idx - board_width - 1][idx] = 1
    if i > 0 and j < board_height - 1: A[idx + board_width - 1][idx] = 1
    if i < board_width - 1 and j > 0:  A[idx - board_width + 1][idx] = 1
    if i < board_width - 1 and j < board_height - 1: A[idx + board_width + 1][idx] = 1

# A couple helpers
def add_rows(A, i, j):  return [(A[i][k] + A[j][k])%2 for k in xrange(n)]
def swap_rows(A, i, j): A[i], A[j] = A[j], A[i]

# The input state to solve
#state = map(int, '1011100111110001100111010')
mat = [map(int, raw_input().split()) for _ in xrange(R)]

state = list(flatten(mat))
G = state[:]
#print state

# Solve via something like Gaussian Elimination
for col in xrange(n):
  # find the first row with a 1 in this column
  for row in xrange(col,n):
    if A[row][col] == 1:
      swap_rows(A, row, col)
      swap_rows(state, row, col)
      for other in xrange(n):
        if other != col and A[other][col] == 1:
          A[other] = add_rows(A, other, col)
          state[other] = state[other] ^ state[col]

# Print out the buttons to be pressed
#for j in xrange(board_height):
#  print ''.join(map(str,state[j*board_width:(j+1)*board_width]))

#for i in xrange(R*C):
#    if state[i]:
#        r, c = divmod(i, C)
#        for dr in [-1, 0, 1]:
#            for dc in [-1, 0, 1]:
#                nr = r + dr
#                nc = c + dc
#                if not (0 <= nr < R and 0 <= nc < C):
#                    continue
#                G[nr*C+nc] = 1 - G[nr*C+nc]
#
#if any(x!=0 for x in G):
#    print 'Impossible'
#    exit(0)

res = state.count(1)
print res