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.Arrays;
import java.util.StringTokenizer;

public class CFC {

    public static void main(String[] args) throws IOException {
        MyScanner sc = new MyScanner(System.in);
        PrintWriter out = new PrintWriter(System.out);
        int N = sc.nextInt();
        int[] a = new int[N];
        for (int i = 0; i < N; i++) a[i] = sc.nextInt();
        int[][] dp = new int[N][N];
        int[][] maximum = new int[N][N];
        for (int start = 0; start < N; start++) {
            int maxOne = 0, maxTwo = 0, max = 0, tempOne = 0, tempTwo = 0;
            for (int i = start; i < N; i++) {
                if (a[i] == 1) {
                    tempOne = tempOne + 1;
                    dp[start][i] = Math.max(maxOne, maxTwo) + 1;
                    maxOne = dp[start][i];
                } else {
                    tempTwo = Math.max(tempOne, tempTwo) + 1;
                    dp[start][i] = maxTwo + 1;
                    maxTwo = maxTwo + 1;
                }
                max = Math.max(max, Math.max(tempOne, tempTwo));
                maximum[start][i] = max;
            }
        }
        int ans = 0;
        for (int i = 0; i < N; i++)
            for (int j = i; j < N; j++) {
                int res = dp[i][j];
                if (i > 0)
                    res += maximum[0][i - 1];
                if (j + 1 < N)
                    res += maximum[j + 1][N - 1];
                ans = Math.max(ans, res);
            }
        out.println(ans);
        out.flush();
        out.close();
    }

    private static class MyScanner {
        StringTokenizer st;
        BufferedReader br;

        public MyScanner(InputStream s) {
            br = new BufferedReader(new InputStreamReader(s));
        }

        public MyScanner(String filename) throws IOException {
            br = new BufferedReader(new FileReader(new File(filename)));
        }

        public String next() throws IOException {
            while (st == null || !st.hasMoreTokens())
                st = new StringTokenizer(br.readLine());
            return st.nextToken();
        }

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

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

        public String nextLine() throws IOException {
            return br.readLine();
        }

        public double nextDouble() throws IOException {
            String x = next();
            StringBuilder sb = new StringBuilder("0");
            double res = 0, f = 1;
            boolean dec = false, neg = false;
            int start = 0;
            if (x.charAt(0) == '-') {
                neg = true;
                start++;
            }
            for (int i = start; i < x.length(); i++)
                if (x.charAt(i) == '.') {
                    res = Long.parseLong(sb.toString());
                    sb = new StringBuilder("0");
                    dec = true;
                } else {
                    sb.append(x.charAt(i));
                    if (dec)
                        f *= 10;
                }
            res += Long.parseLong(sb.toString()) / f;
            return res * (neg ? -1 : 1);
        }

        public boolean ready() throws IOException {
            return br.ready();
        }
    }
}
