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
import math
from collections import defaultdict
n=int(sys.stdin.readline())
arr=list(map(int,sys.stdin.readline().split()))
pre=[0]
cnt1,cnt2=0,0
last1,last2=0,0
for i in range(n):
    if arr[i]==1:
        cnt1+=1
        #pre.append(cnt1)
        x=max(last1+1,0)
        pre.append(x)
        last1=x
    else:
        #cnt2+=1
        x=max(last1+1,last2+1)
        pre.append(x)
        last2=x
suf=[0 for _ in range(n+1)]
#cnt1,cnt2=0,0
last1,last2=0,0
for i in range(n-1,-1,-1):
    if arr[i]==1:
        #cnt1+=1
        x=max(last1+1,last2+1)
        suf[i]=x
        last1=x
    else:
        #cnt2+=1
        x=last2+1
        suf[i]=x
        last2=x
ans=max(max(pre),max(suf))
#print(pre,'pre')
#print(suf,'suf')
#print(ans,'ans')
for i in range(1,n+1):
    cnt1,cnt2=0,0
    last1,last2=0,0
    for j in range(i,n+1):
        if arr[j-1]==1:
            x=max(last1+1,last2+1)
            last1=x
            ans=max(pre[i-1]+x+suf[j],ans)
        else:
            x=last2+1
            last2=x
            ans=max(pre[i-1]+x+suf[j],ans)
print(ans)
