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

SUM1, SUM2 = 0, 0
for i in range(W):
    if A[-2][i]^A[-1][i] == 1:
        SUM1 += 1
for i in range(2):
    if sum(A[(-2)+i])%2 == 1:
        SUM2 += 1

print(sum(A[i][-1] for i in range(H-2))+max(SUM1, SUM2))