N, M = map(int, input().split())
rows = []
for _ in range(N):
    rows.append(list(map(int, input().split())))
sums = [sum(x) for x in rows]

minimum = 1001

for i in range(len(rows)):
    for j in range(len(rows[i])):
        number = rows[i][j]
        if i == 0 and j == 0:
            continue
        if i == len(rows)-1 and j == len(rows[0])-1:
            continue
        if number < minimum:
            minimum = number


if N % 2 == 1 or M % 2 == 1:
    print(sum(sums))
else:
    print(sum(sums)-minimum)

#for i1 in range(N - 1):
#    i2 = i1 + 1

#    current_result = sum(sums) - sums[i1] - sums[i2]

#    for j in range(M - 1):