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.InputStreamReader;
import java.io.IOException;
import java.lang.reflect.Method;
import java.util.*;
import java.io.BufferedReader;
import java.io.PrintWriter;
import java.io.InputStream;
import static java.lang.Math.*;

public class Main {

    public static void main(String[] args) {
        final String[] tasks = new String[]{"D","C","B","A"};
        for(final String task:tasks) {
            try {
                Class ca = Main.class.getClassLoader().loadClass(task);
                if (ca.getField("on").getInt(null) == 1) {
                    Object aTask = ca.newInstance();
                    Method m = ca.getMethod("solve", null);
                    m.invoke(aTask, null);
                }
            } catch (Exception ex) { }
        }
    }

}

class A {
    public static int on = 1;

    public void run(){
        int n = ni();
        int s1 = 0,s2=0,s3=0,s4=0;
        while(n-->0){
            int t = ni();
            if(t==1){
                s1++;
                s3++;
            }else{
                s2++;
                s4++;
            }
            s2 = max(s2,s1);
            s3 = max(s2,s3);
            s4 = max(s3,s4);
        }
        p(s4);

    }




    private InputReader in =  new InputReader(System.in);
    private PrintWriter out = new PrintWriter(System.out);
    public void solve(){run();out.close(); }
    public int ni(){return Integer.parseInt(in.ns());}
    public long nl(){return Long.parseLong(in.ns());}
    public String ns(){return in.ns();}
    public void p(Object obj){out.print(obj);}
    public void pl(Object obj){out.println(obj);}
    public int max(int... args){
        int r = Integer.MIN_VALUE;
        for(int t: args){
            if(t>r){
                r = t;
            }
        }
        return r;
    }
}

class B {
    public static int on = 0;

    public void solve(InputReader in , PrintWriter out){

    }
}

class InputReader {
    private BufferedReader reader;
    private StringTokenizer tokenizer;

    public InputReader(InputStream stream) {
        reader = new BufferedReader(new InputStreamReader(stream), 32768);
        tokenizer = null;
    }

    public String ns() {
        while (tokenizer == null || !tokenizer.hasMoreTokens()) {
            try {
                tokenizer = new StringTokenizer(reader.readLine());
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return tokenizer.nextToken();
    }

}



