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;
        FastScanner in = new FastScanner(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, FastScanner in, PrintWriter out) {
            int n = in.nextInt();
            int[] a = new int[n];
            int[] b = new int[n];
            for (int i = 0; i < n; i++) {
                a[i] = in.nextInt();
                b[n - i - 1] = a[i];
            }
            Info info = new Info(a);
            Info infoRev = new Info(b);
            int ans = info.best(0, n - 1);
            for (int l = 0; l < n; l++) {
                for (int r = l; r < n; r++) {
                    ans = Math.max(ans, info.ones(0, l - 1) + infoRev.best(n - r - 1, n - l - 1) + info.twos(r + 1, n - 1));
                }
            }
            out.println(ans);
        }

        class Info {
            int[] numOnes;
            int[] numTwos;
            int[][] best;

            int ones(int l, int r) {
                if (l > r) {
                    return 0;
                }
                return numOnes[r + 1] - numOnes[l];
            }

            int twos(int l, int r) {
                if (l > r) {
                    return 0;
                }
                return numTwos[r + 1] - numTwos[l];
            }

            int best(int l, int r) {
                if (l > r) {
                    return 0;
                }
                return best[l][r];
            }

            Info(int[] a) {
                int n = a.length;
                numOnes = new int[n + 1];
                numTwos = new int[n + 1];
                for (int i = 0; i < n; i++) {
                    numOnes[i + 1] = numOnes[i] + (a[i] == 1 ? 1 : 0);
                    numTwos[i + 1] = numTwos[i] + (a[i] == 2 ? 1 : 0);
                }
                best = new int[n][n];
                for (int len = 1; len <= n; len++) {
                    for (int l = 0; l + len <= n; l++) {
                        int r = l + len - 1;
                        best[l][r] = 1;
                        if (l < r) {
                            best[l][r] = Math.max(best[l][r], best[l + 1][r] + (a[l] == 1 ? 1 : 0));
                            best[l][r] = Math.max(best[l][r], best[l][r - 1] + (a[r] == 2 ? 1 : 0));
                        }
                    }
                }
            }

        }

    }

    static class FastScanner {
        private BufferedReader in;
        private StringTokenizer st;

        public FastScanner(InputStream stream) {
            in = new BufferedReader(new InputStreamReader(stream));
        }

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

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

    }
}

