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())
A = list(map(int, input().split()))

if n == 1:
    print(1)
    exit()

dp = [[0]*4 for i in range(n)]
if A[0] == 1:
    dp[0][0] += 1
    dp[0][2] += 1
else:
    dp[0][1] += 1
    dp[0][3] += 1
for i in range(1, n):
    if A[i] == 1:
        dp[i][0] = dp[i-1][0]+1
        dp[i][1] = max(dp[i-1][1], dp[i-1][0])
        dp[i][2] = max(dp[i-1][1]+1, dp[i-1][2]+1)
        dp[i][3] = max(dp[i-1][3], dp[i-1][2])
    else:
        dp[i][0] = dp[i-1][0]
        dp[i][1] = max(dp[i-1][0]+1, dp[i-1][1]+1)
        dp[i][2] = max(dp[i-1][2], dp[i-1][1])
        dp[i][3] = max(dp[i-1][2]+1, dp[i-1][3]+1)
print(max(dp[n-1]))
