[2579] 계단 오르기

n = int(input())
score = [0]
for _ in range(n):
    score.append(int(input()))
if n == 1:
    print(score[1])
else:
    dp = [0]*(n+1)
    dp[1] = score[1]
    dp[2] = score[1]+score[2]
    for i in range(3, n+1):
        dp[i] = max(dp[i-3]+score[i-1]+score[i], dp[i-2]+score[i])
    print(dp[n])