N, M = map(int, input().split())

mat = []
for i in range(N):
    mat.append(list(map(int, input().split())))

summa = 0
if N % 2 == 1 or M % 2 == 1:
    for i in mat:
        summa += sum(i)
    print(summa)
elif (N % 2 == 0 and M == 1) or (M % 2 == 0 and N == 1):
    for i in mat:
        summa += sum(i)
    print(summa)
else:
    for i in mat:
        summa += sum(i)
    listSums = []
    for i in range(N):
        for j in range(M):
            if i == 0 and j == 0 or i == N - 1 and j == M - 1:
                continue
            else:
                listSums.append(summa - mat[i][j])
    print(max(listSums))