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.Scanner;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author ZYCSwing
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskC solver = new TaskC();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskC {
        int n;
        int[] one;
        int[] two;

        int subSolve(int l, int r) {
            int tmp = 0;
            for (int i = l - 1; i <= r; ++i) {
                tmp = Math.max(tmp, one[i] - one[l - 1] + two[r] - two[i]);
            }
            return tmp;
        }

        int mySolve(int mid) {
            return subSolve(1, mid) + subSolve(mid + 1, n);
        }

        public void solve(int testNumber, Scanner in, PrintWriter out) {
            n = in.nextInt();
            int[] a = new int[n + 1];
            one = new int[n + 1];
            two = new int[n + 1];
            for (int i = 1; i <= n; ++i) a[i] = in.nextInt();
            for (int i = 1; i <= n; ++i) {
                one[i] = one[i - 1];
                if (a[i] == 1) ++one[i];
            }
            for (int i = 1; i <= n; ++i) {
                two[i] = two[i - 1];
                if (a[i] == 2) ++two[i];
            }

            int res = 0;

            // <= is 1, > is 2
            for (int i = 0; i <= n; ++i) {
                res = Math.max(res, mySolve(i));
            }
            out.println(res);
        }

    }
}

