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 java.util.*;
import java.io.*;

public class Main {
	public static void main(String args[]) {new Main().run();}

	FastReader in = new FastReader();
	PrintWriter out = new PrintWriter(System.out);
	void run(){
		work();
		out.flush();
	}
	long mod=1000000007;
	void work() {
		int n=in.nextInt();
		int[] A=new int[n];
		for(int i=0;i<n;i++) A[i]=in.nextInt();
		int[] one=new int[n];
		int[] two=new int[n];
		int[][] rec=new int[n][n];
		for(int i=0,cur=0;i<n;i++) {
			if(A[i]==1) {
				cur++;
			}
			one[i]=cur;
		}
		for(int i=n-1,cur=0;i>=0;i--) {
			if(A[i]==2) {
				cur++;
			}
			two[i]=cur;
		}
		int ret=0;
		for(int i=0;i<n;i++) {
			int a=0,b=0;
			for(int j=i;j<n;j++) {
				if(A[j]==1) {//逆序
					a=Math.max(a, b)+1;
				}else {
					b++;
				}
				rec[i][j]=Math.max(a, b);
			}
		}
		for(int i=0;i<n;i++) {
			for(int j=i;j<n;j++) {
				ret=Math.max(rec[i][j]+(i==0?0:one[i-1])+(j==n-1?0:two[j+1]), ret);
			}
		}
		out.println(ret);
	}
}



class FastReader
{
	BufferedReader br;
	StringTokenizer st;

	public FastReader()
	{
		br=new BufferedReader(new InputStreamReader(System.in));
	}

	public String next() 
	{
		if(st==null || !st.hasMoreElements())
		{
			try {
				st = new StringTokenizer(br.readLine());
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
		return st.nextToken();
	}

	public int nextInt() 
	{
		return Integer.parseInt(next());
	}

	public long nextLong()
	{
		return Long.parseLong(next());
	}
}