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