rows, columns = [int(j) for j in input().split()]

if rows % 2 == 1 or columns % 2 == 1:
    res = 0
    for _ in range(rows):
        res += sum([int(j) for j in input().split()])
    print(res)
else:
    res = 0
    our_min = -1
    for i in range(rows):
        new_row = [int(j) for j in input().split()]
        res += sum(new_row)
        for j in range(columns):
            if (i + j) % 2 == 1:
                if new_row[j] < our_min or our_min == -1:
                    our_min = new_row[j]
    print(res-our_min)