INF = 10**18

N, M = map(int, input().split())
A = [sum(map(int, input().split())) for _ in range(N)]

dp = [[-INF for j in range(N + 1)] for i in range(N + 1)]

for i in range(N + 1):
    dp[i][0] = 0

for i in range(1, N + 1):
    for j in range(1, N + 1):
        if j % 2 == 0:
            dp[i][j] = max(dp[i][j], dp[i - 1][j], dp[i - 1][j - 1] - A[i - 1])
        else:
            dp[i][j] = max(dp[i][j], dp[i - 1][j], dp[i - 1][j - 1] + A[i - 1])

print(max(dp[N]))