n, m = [int(_) for _ in input().split()]

temp = []
minn = float("inf")
ans = [[] for i in range(n)]
for i in range(n):
    for j,v in enumerate(input().split()):
        ans[i].append(int(v))
        if (i % 2 == 0 and j % 2 == 0) or (i % 2 == 1 and j % 2 == 1):
            continue
        else:
            minn = min(minn,int(v))

summ = sum([sum(v) for v in ans])

if n%2!=0 and m%2!=0:
    print(summ)
else:
    temp.sort()
    print(summ-minn)