N, M = list(map(int, input().split()))
s = 0
best_min = float("inf")
for i in range(N):
    line = list(map(int, input().split()))
    s += sum(line)
    for j in range(M):
        if (i + j) % 2:
            best_min = min(best_min, line[j])

if N % 2 or M % 2:
    print(s)
else:
    print(s - best_min)