N=int(input())
A=list(map(int,input().split()))
L,R=[0],[0]
for i in range(N):
    L.append(A[i*2]-A[i*2+1])
    R.append(A[i*2+1]-A[i*2])
for i in range(1,N+1):
    L[i]+=L[i-1]
    R[i]+=R[i-1]
ans=max(L[i]+R[N]-R[i] for i in range(N+1))
print(ans)