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.StringTokenizer;

public class A {

    FastScanner scanner;
    PrintWriter writer;

    void solve() throws IOException {
        scanner = new FastScanner(System.in);
        writer = new PrintWriter(System.out);

        int n = scanner.nextInt();
        int[] a = new int[n];
        int[] ones = new int[n + 1];
        int[] twos = new int[n + 1];

        for (int i = 0; i < n; i++) {
            a[i] = scanner.nextInt();

            ones[i + 1] = ones[i];
            twos[i + 1] = twos[i];

            if (a[i] == 1) {
                ones[i + 1]++;
            } else {
                twos[i + 1]++;
            }
        }

        int ans = 0;

        for (int i = 0; i < n; i++) {
            ans = Math.max(ans, count(ones, 0, i) + count(twos, i, n));

            int d = 0;

            for (int j = i + 1; j <= n; j++) {
                if (a[j - 1] == 1) {
                    d = Math.max(d + 1, count(twos, i, j) + 1);
                }

                int t = Math.max(d, count(twos, i, j));

                ans = Math.max(ans, count(ones, 0, i) + t + count(twos, j, n));
            }
        }

        writer.println(ans);

        writer.close();
    }

    int count(int[] a, int l, int r) {
        return a[r] - a[l];
    }

    public static void main(String... args) throws IOException {
        new A().solve();
    }

    static class FastScanner {

        BufferedReader br;
        StringTokenizer tokenizer;

        FastScanner(String fileName) throws FileNotFoundException {
            this(new FileInputStream(new File(fileName)));
        }

        FastScanner(InputStream is) {
            br = new BufferedReader(new InputStreamReader(is));
        }

        String nextLine() throws IOException {
            tokenizer = null;
            return br.readLine();
        }

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

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

        double nextDouble() throws IOException {
            return Double.parseDouble(next());
        }
    }
}
