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

from collections import deque

d = deque()
d.append([False, 0])

for i in range(N):
    dd = deque()
    while len(d) > 0:
        v = d.pop()
        if v[0] :
            dd.append([False, v[1]])
        else:
            dd.append([True, v[1]+V[i]])
            dd.append([False, v[1]])
    d = dd
print(max(d)[1])