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.
"""Codeforces P934C. A Twisty Movement (=P933A)
    (http://codeforces.com/problemset/problem/934/C)

Problem tags : brute force, dp

Hint: Same as finding the longest subsequence of 
       [1, ..., 1, 2, ..., 2, 1, ..., 1, 2, ..., 2]
Time Complexity: O(n)
"""

def main():
    n = int(input())
    a = [int(x) for x in input().split()]
    
    val = [1, 2, 1, 2]
    # max_len[i] : length of longest sequence of 
    # [ val[0] * (n0), val[1] * (n1), ... , val[i] * (ni) ]
    max_len = [0, 0, 0, 0]
    for x in a:
        for i in range(4):
            if x == val[i]:
                max_len[i] += 1
            if i > 0:
                max_len[i] = max(max_len[i - 1], max_len[i])
    print(max_len[-1])
     
    
if __name__ == '__main__':
    main()
    