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.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.StringTokenizer;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TwistyMovement solver = new TwistyMovement();
        solver.solve(1, in, out);
        out.close();
    }

    static class TwistyMovement {
        public void solve(int testNumber, InputReader in, PrintWriter out) {
            int N = in.nextInt();
            int[][] dp = new int[N][N];
            int[] pref = new int[N];
            int[] arr = new int[N];
            int cnt = 0;
            for (int i = 0; i < N; i++) {
                if (in.nextInt() == 1) {
                    pref[i] = 1;
                    arr[i] = 1;
                } else {
                    pref[i] = -1;
                    arr[i] = -1;
                    cnt++;
                }
                if (i > 0) {
                    pref[i] += pref[i - 1];
                }
            }
            for (int i = 0; i < N; i++) {
                dp[i][i] = pref[i];
                if (i < N - 1) {
                    dp[i][i + 1] = Math.max(pref[i + 1], pref[i] - arr[i] + arr[i + 1]);
                }
            }
            for (int sz = 3; sz <= N; sz++) {
                for (int i = 0; i + sz - 1 < N; i++) {
                    dp[i][i + sz - 1] = Math.max(dp[i + 1][i + sz - 2] + arr[i + sz - 1] - arr[i], Math.max(pref[i] - arr[i] + arr[i + sz - 1], pref[i + sz - 1]));
                }
            }
            int res = 0;
            for (int i = 0; i < N; i++) {
                for (int j = i; j < N; j++) {
                    res = Math.max(dp[i][j], res);
                }
            }
            out.println(res + cnt);
        }

    }

    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

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

    }
}

