import sys
input=sys.stdin.readline
def I(): return int(input())
def MI(): return map(int, input().split())
def LI(): return list(map(int, input().split()))

def main():
    mod=10**9+7
    N,M=MI()
    A=[0]*N
    for i in range(N):
        a=LI()
        A[i]=sum(a)
    
    dp=[[0]*3 for _ in range(N)]
    # dp[i][j]はi個目まで見た時のmax,j=0,1でi個目が+,-
    
    dp[0][0]=A[0]
    
    for i in range(1,N):
        
        
        for j in range(i):
            dp[i][0]=max(dp[i][0], dp[j][1]+A[i],A[i])
            dp[i][1]=max(dp[i][1], dp[j][0]-A[i])
            

    ans=0
    for i in range(N):
        ans=max(ans,dp[i][0])
        
    print(ans)
        
        
        
            
    


main()