N,M = map(int,input().split())
A = []
for _ in range(N):
    A.append(sum(list(map(int,input().split()))))
ans = 0
if N == 1:
    print(A[0])
    exit()
ac = [A[0]]
for i in range(1,N):
    if i%2 == 0:
        ac.append(ac[-1]+A[i])
    else:
        ac.append(ac[-1]-A[i])
ac = [0]+ac
print(ac)
for i in range(len(ac)):
    for j in range(i+1,len(ac)):
        ans = max(ans,abs(ac[j]-ac[i]))
print(ans)