题解 | #最小花费爬楼梯#

import sys

# for line in sys.stdin:
#     a = line.split()
#     print(int(a[0]) + int(a[1]))
n = int(input())
cost = list( map(int,input().split()))



dp = [0 for i in range(n+1)]
# dp[0] = 0
# dp[1] =cost[0]
for i in range(2,n+1):
  #到第i阶台阶所需要的花费，dp表示
    dp[i]=min(dp[i-2]+cost[i-2],dp[i-1]+cost[i-1])
print(max(dp))