dxdy = (
    (0, 0),
    (0, 1), (1, 0), (-1, 0), (0, -1),
    (1, 1), (-1, 1), (1, -1), (-1, -1),
)
H, W = map(int, input().split())
G = list(list(map(int, input().split())) for _ in range(H))
A = [[0] * W for _ in range(H)]

answer = 10 ** 10
L = H + W - 1
for bit in range(1 << L):
    #copy
    for i in range(H):
        for j in range(W):
            A[i][j] = G[i][j]

    #initial state
    res = [[0] * W for _ in range(H)]
    x = 0
    for i in range(H):
        if (bit >> x) & 1:
            res[i][0] = 1
        x += 1
    for j in range(1, W):
        if (bit >> x) & 1:
            res[0][j] = 1
        x += 1
   
    for i in range(H):
        for dx, dy in dxdy:
            nx = i + dx
            ny = dy
            if 0 <= nx < H and 0 <= ny < W:
                A[nx][ny] ^= res[i][0]
    for j in range(1, W):
        for dx, dy in dxdy:
            nx = dx
            ny = j + dy
            if 0 <= nx < H and 0 <= ny < W:
                A[nx][ny] ^= res[0][j]
   
    #残りを構築
    for i in range(1, H):
        for j in range(1, W):
            res[i][j] = A[i - 1][j - 1]
            for dx, dy in dxdy:
                nx = i + dx
                ny = j + dy
                if 0 <= nx < H and 0 <= ny < W:
                    A[nx][ny] ^= res[i][j]
   
    #OKか確認
    if sum(sum(a) for a in A) == 0:
        cnt = sum(sum(r) for r in res)
        if answer > cnt:
            answer = cnt
            # print(bit, bin(bit)[2:].zfill(L))
            # print(*A, sep="\n")
            # print(sum(sum(r) for r in res))
            # print(*res, sep="\n")
            # print("------------------------------------")
               
if answer >= 10 ** 10:
    print(-1)
else:
    print(answer)