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

DP=[0 for i in range(N+1)]
DP[1]=V[0]
DP[2]=V[1]

for i in range(2,N):
##    print(i,max(DP[:i]))
    DP[i+1]=max(DP[:i])+V[i] if max(DP[:i])+V[i]>max(DP[:i]) else max(DP[:i])

print(DP[N])