n, m = map(int, input().split())
a = [list(map(int, input().split())) for i in range(n)]
INF = 10 ** 22


b = [sum(a[i]) for i in range(n)]


dp = [[-INF] * (n + 1) for i in range(n + 1)]
dp[0][0] = 0

for i in range(n):
    val = b[i]
    for j in range(n + 1):
        dp[i + 1][j] = max(dp[i][j], dp[i + 1][j])
        if j + 1 > n:
            continue
        if (j + 1) % 2 == 1:
            dp[i + 1][j + 1] = max(dp[i][j] + val, dp[i + 1][j + 1])
        else:
            dp[i + 1][j + 1] = max(dp[i][j] - val, dp[i + 1][j + 1])
            

print(max(dp[-1]))