def main():
    import sys
    input = sys.stdin.readline

    N = int(input())
    A = list(map(int, input().split()))

    left = [0] * (N+1)
    right = [0] * (N+1)
    for i in range(N):
        h = i*2
        t = i*2+1
        left[i+1] = left[i] + A[h] - A[t]
    for i in range(N):
        h = 2*N - 1 - i*2
        t = 2*N - 2 - i*2
        right[N-i-1] = right[N-i] + A[h] - A[t]
    ans = -10**10
    for i in range(N+1):
        ans = max(ans, left[i] + right[i])
    print(ans)

if __name__ == '__main__':
    main()