n = int(input())
a = []
a.append(0)
a[1:] = [int(x) for x in input().split()]

x = [0 for _ in range(n + 2)]
y = [0 for _ in range(n + 2)]


for i in range(n):
    x[i + 1] = y[i] + a[i + 1]
    y[i + 1] = max(x[i],y[i])

print(max(x[n],y[n]))