"""回転寿司""" N = int(input()) V = list(map(int, input().split())) if N == 1: print(V[0]) else: v = [0] * (N+10) max_go_back_two = V[0] v[0] = V[0] v[1] = V[1] for i in range(2, N): v[i] = max(max_go_back_two + V[i], V[i]) max_go_back_two = max(max_go_back_two, v[i-1]) print(max(v))