n, m = map(int, input().split())
a = [sum(list(map(int, input().split()))) for i in range(n)]
a.sort(reverse=True)
cnt = 0
l = []
for i in range(n):
    if i % 2 == 0:
        cnt += a[i]
    else:
        cnt -= a[i]
    l.append(cnt)
print(max(l))