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 Main {

    static int[][] memo;
    static int[] a;

    static int dp(int i, int j) {
        if(i > j)
            return 0;
        if(memo[i][j] != -1)
            return memo[i][j];
        int x = a[i] == 2 ? 1 : 0, y = a[j] == 1 ? 1 : 0;
        return memo[i][j] =  Math.max(x + dp(i + 1, j), y + dp(i, j - 1));
    }
    public static void main(String[] args) throws IOException {
        Scanner sc = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);
        int n = sc.nextInt(), ones[] = new int[n], twos[] = new int[n];
        a = new int[n];
        for(int i = 0; i < n; ++i) {
            a[i] = sc.nextInt();
            ones[i] = (a[i] & 1) + (i > 0 ? ones[i - 1] : 0);
            twos[i] = a[i] >> 1;
        }
        for(int i = n - 2; i >= 0; --i)
            twos[i] += twos[i + 1];

        memo = new int[n][n];
        for(int[] x: memo)
            Arrays.fill(x, -1);
        int ans = 0;
        for(int i = 0; i < n; ++i)
            for(int j = i; j < n; ++j) {
                int outer = (i > 0 ? ones[i - 1] : 0) + (j < n - 1 ? twos[j + 1] : 0);
                ans = Math.max(ans, outer + dp(i, j));
            }
        out.println(ans);
        out.close();
    }

    static class Scanner
    {
        StringTokenizer st;
        BufferedReader br;

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

        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());}
    }
}