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.Arrays;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author warez80
 */
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);
        TaskC solver = new TaskC();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskC {
        private int n;
        private int[] a;
        long[][][] memo;

        public void solve(int testNumber, FastScanner in, PrintWriter out) {
            n = in.nextInt();
            a = in.nextInts(n);
            memo = new long[3][4][n];
            for (long[][] x : memo) for (long[] y : x) Arrays.fill(y, -1);
            out.println(go(0, 0, 0));
        }

        long go(int last, int phase, int idx) {
            if (idx == n) return 0;
            long ans = 0;
            if (memo[last][phase][idx] != -1) return memo[last][phase][idx];
            switch (phase) {
                case 0: {
                    ans = Math.max(1 + go(a[idx], 1, idx + 1), go(last, 0, idx + 1));
                    break;
                }
                case 1: {
                    ans = go(last, 1, idx + 1);
                    if (last <= a[idx]) {
                        ans = Math.max(ans, 1 + go(a[idx], 1, idx + 1));
                    }
                    ans = Math.max(ans, go(last, 2, idx));
                    break;
                }
                case 2: {
                    ans = go(last, 2, idx + 1);
                    if (last >= a[idx]) {
                        ans = Math.max(ans, 1 + go(a[idx], 2, idx + 1));
                    }
                    ans = Math.max(ans, go(last, 3, idx));
                    break;
                }
                case 3: {
                    ans = go(last, 3, idx + 1);
                    if (last <= a[idx]) {
                        ans = Math.max(ans, 1 + go(a[idx], 3, idx + 1));
                    }
                    break;
                }
            }
            return memo[last][phase][idx] = ans;
        }

    }

    static class FastScanner {
        private byte[] buffer = new byte[1 << 10];
        private int bp;
        private int br;
        private InputStream is;
        private boolean empty;
        private boolean skipLF;

        public FastScanner(InputStream in) {
            is = in;
        }

        private byte r() {
            if (empty) throw new UnknownError();
            if (bp == br) try {
                br = is.read(buffer, bp = 0, 1 << 10);
                if (br == -1) buffer[0] = -1;
            } catch (Exception e) {
            }
            if (bp >= buffer.length || buffer[bp] == -1) {
                empty = true;
                return -1;
            }
            return buffer[bp++];
        }

        private byte rnw() {
            skipLF = false;
            byte c;
            do c = r(); while (c <= ' ');
            return c;
        }

        public int nextInt() {
            int ret = 0;
            byte c = rnw();
            boolean neg = c == '-';
            if (neg) c = r();
            do ret = (ret << 3) + (ret << 1) + c - '0'; while ((c = r()) >= '0' && c <= '9');
            if (neg) return -ret;
            return ret;
        }

        public int[] nextInts(int count) {
            int[] xs = new int[count];
            for (int i = 0; i < count; i++) {
                xs[i] = nextInt();
            }
            return xs;
        }

    }
}

