✅ 정답 공개
n = int(input())
s = list(map(int, input().split()))
if n == 1:
print(s[0])
elif n == 2:
print(s[0]+s[1])
else:
dp = [0]*n
dp[0] = s[0]
dp[1] = s[0]+s[1]
dp[2] = max(s[0]+s[2], s[1]+s[2])
for i in range(3, n):
dp[i] = max(dp[i-2]+s[i], dp[i-3]+s[i-1]+s[i])
print(dp[n-1])