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

public class Codeforces933A {
	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st = new StringTokenizer(br.readLine());
		int n = Integer.parseInt(st.nextToken());
		
		int[] a = new int[n];
		st = new StringTokenizer(br.readLine());
		for (int i = 0; i < n; i++) {
			a[i] = Integer.parseInt(st.nextToken());
		}
		
		int[] one = new int[n];
		int[] onetwo = new int[n];
		int[] onetwoone = new int[n];
		int[] onetwoonetwo = new int[n];
		
		if (a[0] == 1) {
			one[0] = 1;
		}
		onetwo[0] = 1;
		onetwoone[0] = 1;
		onetwoonetwo[0] = 1;
		
		for (int i = 1; i < n; i++) {
			if (a[i] == 1) {
				one[i] = one[i-1]+1;
				onetwo[i] = Math.max(one[i], onetwo[i-1]);
				onetwoone[i] = onetwoone[i-1]+1;
				onetwoonetwo[i] = Math.max(onetwoone[i], onetwoonetwo[i-1]);
			}
			else {
				one[i] = one[i-1];
				onetwo[i] = onetwo[i-1]+1;
				onetwoone[i] = Math.max(onetwoone[i-1], onetwo[i]);
				onetwoonetwo[i] = onetwoonetwo[i-1]+1;
			}
		}
		System.out.println(onetwoonetwo[n-1]);
	}	
}
