# from bisect import bisect_left

n, m = map(int, input().split())
arr = [list(map(int, input().split())) for _ in range(n)]

sumVal = 0
for i in range(n):
    sumVal += sum(arr[i])

if (n % 2 != 0 or m % 2 != 0):
    print(sumVal)
    
minFound = pow(10, 10)
for i in range(n):
    for j in range(n):
        if (i % 2 != j % 2):
            minFound = min(minFound, arr[i][j])
print( sumVal - minFound )