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.
# n = int(input().strip())
# res = list()
# while n > 0:
#     if n >= 2:
#         res.append(8)
#         n -= 2
#     elif n == 1:
#         res.append(6)
#         n -= 1
# if len(res) > 18:
#     print('-1')
# else:
#     print(''.join(map(str, res)))

n = int(input().strip())
a = list(map(int, input().strip().split()))
ones = [0] * (n+1)
twos = [0] * (n+1)
for i in range(n):
    ones[i+1] = ones[i] if a[i] == 2 else ones[i] + 1
    twos[i+1] = twos[i] if a[i] == 1 else twos[i] + 1

if twos[n] == 0:
    print(n)
    exit(0)

res = 0
for i in range(n):
    best1 = 0
    for j in range(i+1):
        c1 = ones[j]
        c2 = twos[i+1] - twos[j]
        best1 = max(best1, c1 + c2)
    best2 = 0
    for j in range(i+1, n+1):
        d1 = ones[j] - ones[i+1]
        d2 = twos[n] - twos[j]
        best2 = max(best2, d1 + d2)
    res = max(res, best1 + best2)
print(res)