H, W = map(int, input().split())
A = [list(map(int, input().split())) for _ in range(H)]

for i in range(H-2):
    for j in range(W-1):
        if A[i][j] == 1:
            for k in range(2):
                for l in range(2):
                    A[i+k][j+l] ^= 1
for i in range(W-2):
    if A[-2][i] == A[-1][i] == 1:
        for j in range(2):
            for k in range(2):
                A[(-2)+j][i+k] ^= 1

if 3 <= A[-2][-2]+A[-2][-1]+A[-1][-2]+A[-1][-1]:
    for j in range(2):
        for k in range(2):
            A[(-2)+j][(-2)+k] ^= 1

print(sum(sum(a) for a in A))