# hamster

def line_ints(): return list(map(int, input().strip().split()))

def odd(i):
    return i % 2 == 1

def even(j):
    return not odd(j)

n, m = line_ints()

if odd(n) or odd(m):
    s = 0
    for i in range(n):
        line = line_ints()
        for j, num in enumerate(line):
            s += num

    print(s)
else:
    min_num = 1001
    s = 0
    for i in range(n):
        line = line_ints()
        for j, num in enumerate(line):
            s += num
            if (odd(i) and even(j)) or (even(i) and odd(j)):
                min_num = min(min_num, num)
    
    print(s - min_num)