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.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.PrintStream;
import java.util.*;


public class Main {
    static Scanner sc = new Scanner(new BufferedInputStream(System.in));
    static PrintStream out = new PrintStream(new BufferedOutputStream(System.out, 8192));
    static int n;
    static int N = 2010;
    static int[] arr = new int[N];
    static int[][] dp = new int[N][4];

    public static void main(String[] args) {
        n = Integer.parseInt(sc.nextLine());
        String[] in = sc.nextLine().split(" ");
        for (int i = 0; i < n; i++) {
            arr[i + 1] = Integer.parseInt(in[i]);
        }
        for (int i = 1; i <= n; i++) {
            dp[i][0] = dp[i - 1][0] + (arr[i] == 1 ? 1 : 0);
            dp[i][1] = Math.max(dp[i - 1][0], dp[i - 1][1]) + (arr[i] == 2 ? 1 : 0);
            dp[i][2] = Math.max(dp[i - 1][1], dp[i - 1][2]) + (arr[i] == 1 ? 1 : 0);
            dp[i][3] = Math.max(dp[i - 1][3], dp[i - 1][2]) + (arr[i] == 2 ? 1 : 0);
        }
        int max = 0;
        for (int i = 0; i < 4; i++) {
            max = Math.max(dp[n][i], max);
        }
        out.println(max);
        sc.close();
        out.close();
    }
}