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

dpMax=[0 for i in range(N)]
dpMin=[0 for i in range(N)]
dpMax[-1]=A[-1]
dpMin[-1]=0

for i in range(N-2,-1,-1):
    dpMax[i]=max(dpMax[i+1],A[i]-dpMin[i+1])
    dpMin[i]=min(dpMin[i+1],A[i]-dpMax[i+1])

print(dpMax[0])