A dragon symbolizes wisdom, power and wealth. On Lunar New Year's Day, people model a dragon with bamboo strips and clothes, raise them with rods, and hold the rods high and low to resemble a flying dragon.

A performer holding the rod low is represented by a 1, while one holding it high is represented by a 2. Thus, the line of performers can be represented by a sequence a1, a2, ..., an.

Little Tommy is among them. He would like to choose an interval [l, r] (1 ≤ l ≤ r ≤ n), then reverse al, al + 1, ..., ar so that the length of the longest non-decreasing subsequence of the new sequence is maximum.

A non-decreasing subsequence is a sequence of indices p1, p2, ..., pk, such that p1 < p2 < ... < pk and ap1 ≤ ap2 ≤ ... ≤ apk. The length of the subsequence is k.

Input

The first line contains an integer n (1 ≤ n ≤ 2000), denoting the length of the original sequence.

The second line contains n space-separated integers, describing the original sequence a1, a2, ..., an (1 ≤ ai ≤ 2, i = 1, 2, ..., n).

Output

Print a single integer, which means the maximum possible length of the longest non-decreasing subsequence of the new sequence.

Examples

Input

4
1 2 1 2


Output

4


Input

10
1 1 2 2 2 1 1 2 2 1


Output

9

Note

In the first example, after reversing [2, 3], the array will become [1, 1, 2, 2], where the length of the longest non-decreasing subsequence is 4.

In the second example, after reversing [3, 7], the array will become [1, 1, 1, 1, 2, 2, 2, 2, 2, 1], where the length of the longest non-decreasing subsequence is 9.
import sys


def input():
    return sys.stdin.buffer.readline().rstrip()


n = int(input())
a = list(map(int, input().split()))
ans = max(a.count(1), a.count(2))
#mixed case
prefix = [0]*(n + 10)
suffix = [0]*(n + 10)
for i in range(n):
    if a[i] == 1:
        prefix[i + 1] = 1

a.reverse()
for i in range(n):
    if a[i] == 2:
        suffix[i + 1] = 1
a.reverse()

for i in range(n):
    prefix[i + 1] += prefix[i]
    suffix[i + 1] += suffix[i]

INF = 1 << 60
a.reverse()
ans = -INF


for l in range(n):
    max_case_1 = 0
    max_case_2 = 0
    for r in range(l, n):
        if a[r] == 1:
            max_case_1 += 1
        elif a[r] == 2:
            max_case_2 = max(max_case_2, max_case_1) + 1
        K = max(max_case_1, max_case_2)
        ans = max(ans, K + prefix[n - 1 - r] + suffix[l])

print(ans)

