
https://www.acmicpc.net/problem/2579
n=int(input())
num=[0]*301
dp=[0]*301
for i in range(n):
num[i]=int(input())
dp[0]=num[0]
dp[1]=num[0]+num[1]
dp[2]=max(num[0]+num[2],num[1]+num[2])
for i in range(3,n):
dp[i]=max(num[i]+dp[i-3]+num[i-1],num[i]+dp[i-2])
print(dp[n-1])