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.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.StringTokenizer;

public class WorkFile {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(reader.readLine());
        StringTokenizer sToken = new StringTokenizer(reader.readLine());
        int[] arr = new int[n];
        int[] ones = new int[n];
        int one = 0;
        for (int i=0; i<n; i++) {
            arr[i] = Integer.parseInt(sToken.nextToken());
            if (arr[i]==1) one++;
            ones[i] = one;
        }
        int[] twos = new int[n];
        int two = 0;
        for (int i=n-1; i>-1; i--) {
            if (arr[i]==2) two++;
            twos[i] = two;
        }
        int ans = Math.max(one, two);
        for (int i=0; i<n-1; i++) {
            if (arr[i]==2 && arr[i+1]==1) {
                int a = 0, maxleft = 0;
                for (int j=i; j>-1; j--) {
                    if (arr[j]==2) a++;
                    else a--;
                    maxleft = Math.max(maxleft, a);
                }
                int b = 0, maxright = 0;
                for (int j=i+1; j<n; j++) {
                    if (arr[j]==1) b++;
                    else b--;
                    maxright = Math.max(maxright, b);
                }
                ans = Math.max(ans, ones[i]+maxright+twos[i+1]+maxleft);
            } else ans = Math.max(ans, ones[i]+twos[i+1]);
        }
        PrintWriter writer = new PrintWriter(System.out);
        writer.print(ans);
        writer.close();
    }
}