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.*;
import java.math.BigInteger;
import java.util.Map.Entry;

import static java.lang.Math.*;

public class A extends PrintWriter {

    void run() {
        int n = nextInt();
        int[] a = nextArray(n);

        int[] cnt1 = new int[n + 1];
        int[] cnt2 = new int[n + 1];

        for (int i = 1; i <= n; i++) {
            cnt1[i] = cnt1[i - 1];
            cnt2[i] = cnt2[i - 1];

            if (a[i - 1] == 1) {
                ++cnt1[i];
            } else {
                ++cnt2[i];
            }
        }

        int ans = 0;

        for (int m = 0; m <= n; m++) {
            ans = max(ans, cnt1[m] - cnt1[0] + cnt2[n] - cnt2[m]);
        }

        int[][] dp = new int[n + 1][n + 1];

        for (int i = 0; i <= n; i++) {
            dp[i][i] = 1;
        }

        for (int len = 1; len < n; len++) {
            for (int l = 1; l <= n; l++) {
                int r = l + len;
                if (r <= n) {
                    if (a[r - 1] == 1) {
                        dp[l][r] = dp[l][r - 1] + 1;
                    } else {
                        dp[l][r] = max(dp[l][r - 1], cnt2[r] - cnt2[l - 1]);
                    }
                }
            }
        }

        for (int l = 1; l <= n; l++) {
            for (int r = l; r <= n; r++) {
                ans = max(ans, cnt1[l - 1] - cnt1[0] + cnt2[n] - cnt2[r] + dp[l][r]);

                // printf("%2d %2d %2d %2d %2d %2d %2d %2d%n", l, r, cnt1[l - 1], cnt1[0], cnt2[n], cnt2[r], dp[l][r], ans);
                // printf("%2d %2d %2d%n", l, r, dp[l][r]);
            }
        }

        println(ans);

    }

    boolean skip() {
        while (hasNext()) {
            next();
        }
        return true;
    }

    int[][] nextMatrix(int n, int m) {
        int[][] matrix = new int[n][m];
        for (int i = 0; i < n; i++)
            for (int j = 0; j < m; j++)
                matrix[i][j] = nextInt();
        return matrix;
    }

    String next() {
        while (!tokenizer.hasMoreTokens())
            tokenizer = new StringTokenizer(nextLine());
        return tokenizer.nextToken();
    }

    boolean hasNext() {
        while (!tokenizer.hasMoreTokens()) {
            String line = nextLine();
            if (line == null) {
                return false;
            }
            tokenizer = new StringTokenizer(line);
        }
        return true;
    }

    int[] nextArray(int n) {
        int[] array = new int[n];
        for (int i = 0; i < n; i++) {
            array[i] = nextInt();
        }
        return array;
    }

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

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

    double nextDouble() {
        return Double.parseDouble(next());
    }

    String nextLine() {
        try {
            return reader.readLine();
        } catch (IOException err) {
            return null;
        }
    }

    public A(OutputStream outputStream) {
        super(outputStream);
    }

    static BufferedReader reader;
    static StringTokenizer tokenizer = new StringTokenizer("");
    static Random rnd = new Random();
    static boolean OJ;

    public static void main(String[] args) throws IOException {
        OJ = System.getProperty("ONLINE_JUDGE") != null;
        A solution = new A(System.out);
        if (OJ) {
            reader = new BufferedReader(new InputStreamReader(System.in));
            solution.run();
        } else {
            reader = new BufferedReader(new FileReader(new File(A.class.getName() + ".txt")));
            long timeout = System.currentTimeMillis();
            while (solution.hasNext()) {
                solution.run();
                solution.println();
                solution.println("----------------------------------");
            }
            solution.println("time: " + (System.currentTimeMillis() - timeout));
        }
        solution.close();
        reader.close();
    }
}