n=int(input())
v=list(map(int,input().split()))
dp=[[0]*2 for i in range(n+1)]
for i in range(n):
  for j in range(n):
    dp[i+1][0]=max(dp[i+1][0],dp[i][0],dp[i][1])
    dp[i+1][1]=max(dp[i+1][1],dp[i][0]+v[i])
print(max(dp[-1]))