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;
        MyScan in = new MyScan(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskA solver = new TaskA();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskA {
        public void solve(int testNumber, MyScan in, PrintWriter out) {
            int n = in.nextInt();
            int[] d = in.na(n);

            int[][][] ans1 = new int[n][n][2];

            int[] ll = new int[n + 1];
            int[] oo = new int[n + 1];

            for (int s = 0; s < n; s++) {
                ll[s + 1] = ll[s];
                oo[n - s - 1] = oo[n - s];
                if (d[s] == 1) {
                    ll[s + 1]++;
                }
                if (d[n - s - 1] == 2) {
                    oo[n - s - 1]++;
                }

            }

            for (int l = n - 1; l >= 0; l--) {
                int h1 = 0;
                int h2 = 0;
                for (int r = l; r >= 0; r--) {
                    if (d[r] == 1) {
                        h1++;
                    } else {
                        h2 = Math.max(h2, h1) + 1;
                    }
                    ans1[l][r][0] = h1;
                    ans1[l][r][1] = h2;
                }
            }
            int ans = 0;
            for (int r = 0; r < n; r++) {
                for (int s = r + 1; s <= n; s++) {
                    int cur = ll[r] + oo[s] + Math.max(ans1[s - 1][r][0], ans1[s - 1][r][1]);
                    ans = Math.max(ans, cur);
                }
            }

            out.println(ans);

        }

    }

    static class MyScan {
        BufferedReader br;
        StringTokenizer st;

        MyScan(BufferedReader br) {
            this.br = br;
        }

        public MyScan(InputStream in) {
            this(new BufferedReader(new InputStreamReader(in)));
        }

        public void findToken() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
        }

        public String next() {
            findToken();
            return st.nextToken();
        }

        public int[] na(int n) {
            int[] k = new int[n];
            for (int i = 0; i < n; i++) {
                k[i] = fi();
            }
            return k;
        }

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

        public int fi() {
            String t = next();
            int cur = 0;
            boolean n = t.charAt(0) == '-';
            for (int a = n ? 1 : 0; a < t.length(); a++) {
                cur = cur * 10 + t.charAt(a) - '0';
            }
            return n ? -cur : cur;
        }

    }
}

