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.*;
public class Main {
    public static void main(String args[]){
        FastReader input=new FastReader();
        PrintWriter out=new PrintWriter(System.out);
        int T=1;
        while(T-->0)
        {
            int n=input.nextInt();
            int a[]=new int[n];
            int o=0,t=0;
            for(int i=0;i<n;i++)
            {
                a[i]=input.nextInt();
                if(a[i]==1)
                {
                    o++;
                }
                else
                {
                    t++;
                }
            }
            int c=1;
            ArrayList<Integer> l=new ArrayList<>();
            for(int i=0;i<n-1;i++)
            {
                if(a[i]!=a[i+1])
                {
                    l.add(c);
                    c=1;
                }
                else
                {
                    c++;
                }
            }
            l.add(c);
            ArrayList<Integer> ones=new ArrayList<>();
            ArrayList<Integer> twos=new ArrayList<>();
            int x=0;
            int y=1;
            if(a[0]!=1)
            {
                ones.add(0);
                x++;
                y=0;
            }
            for(int i=x;i<l.size();i+=2)
            {
                ones.add(l.get(i));
            }
            for(int i=y;i<l.size();i+=2)
            {
                twos.add(l.get(i));
            }
            if(a[n-1]==1)
            {
                twos.add(0);
            }
            int dp[][][]=new int[2][ones.size()][4];
            for(int j=0;j<ones.size();j++)
            {
                for(int i=0;i<2;i++)
                {
                    if(i==0 && j==0)
                    {
                        dp[i][j][0]=ones.get(0);
                    }
                    else if(i==1 && j==0)
                    {
                        dp[i][j][1]=dp[0][0][0]+twos.get(j);
                    }
                    else
                    {
                        if(i==0)
                        {
                            dp[i][j][0]=dp[i][j-1][0]+ones.get(j);
                            dp[i][j][2]=Math.max(dp[i][j-1][2],dp[1][j-1][1])+ones.get(j);
                        }
                        else
                        {
                            dp[i][j][1]=Math.max(dp[0][j][0],dp[i][j-1][1])+twos.get(j);
                            dp[i][j][3]=Math.max(dp[0][j][2],dp[i][j-1][3])+twos.get(j);
                        }
                    }
                }
            }
            out.println(Math.max(dp[1][ones.size()-1][1],dp[1][ones.size()-1][3]));
        }
        out.close();
    }
    static class FastReader
    {
        BufferedReader br;
        StringTokenizer st;
        public FastReader()
        {
            br = new BufferedReader(new InputStreamReader(System.in));
        }
        String next()
        {
            while (st == null || !st.hasMoreElements())
            {
                try
                {
                    st = new StringTokenizer(br.readLine());
                }
                catch (IOException e)
                {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }
        int nextInt()
        {
            return Integer.parseInt(next());
        }
        long nextLong()
        {
            return Long.parseLong(next());
        }
        double nextDouble()
        {
            return Double.parseDouble(next());
        }
        String nextLine()
        {
            String str="";
            try
            {
                str=br.readLine();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
            return str;
        }
    }
}