N=int(input())
V=list(map(int,input().split()))

dp=[0]*N
ep=[0]*N
dp[0]=V[0]
for i in range(1,N):
    dp[i]=ep[i-1]+V[i]
    ep[i]=max(dp[i-1],ep[i-1])
print(max(dp[-1],ep[-1]))