n = int(input())
a = list(map(int, input().split()))
l = []
i = 0
while i < n:
    cnt = 1
    while i < n - 1 and a[i] == a[i + 1]:
        cnt += 1
        i += 1
    l.append(cnt)
    i += 1
m = len(l)
dp = [[0] * (m + 1) for _ in range(2)]
dp[0][0] = 0
for i in range(m):
    dp[1][i + 1] = dp[0][i] + l[i]
    dp[0][i + 1] = max(dp[0][i], dp[1][i])
print(max(dp[0][m], dp[1][m]))