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.InputStream;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.StringTokenizer;

public class C {

	public static void main(String[] args) throws IOException {
		Scanner sc=new Scanner(System.in);
		int n=sc.nextInt();
		int []a=new int [n];
		int []v=new int [n];
		int twos=0;
		for(int i=0;i<n;i++)
			a[i]=sc.nextInt();
		for(int x:a)
			if(x==2)
				twos++;
		/*int []maxP=new int [n];*/
		
		
		int last=twos;
		int ans=twos;
		int remTwos=twos;
		for(int i=0;i<n;i++)
		{
			if(a[i]==1)
			{
				v[i]=last+1;
				last=v[i];
				ans=Math.max(ans, v[i]);
			}
			else
			{	
				
				v[i]=remTwos--;
				last--;
			}	
		}
		
			
		
		int maxP=v[0];
		for(int i=0;i<n;i++)
		{
			
			maxP=Math.max(maxP, v[i]);
			int max=maxP;
			int extra=0;
			for(int j=i+1;j<n;j++)
			{
				if(a[j]==1)
				{
					max++;
					extra--;
					
				}
				else
				{	
					extra++;
					max--;
				}	
				max=Math.max(max, v[j]+extra);
				ans=Math.max(ans, max);
				
			}
		}
		System.out.println(ans);
			

	}
	static class Scanner
	{
		BufferedReader br;
		StringTokenizer st;
		public Scanner(InputStream s)
		{
			br=new BufferedReader(new InputStreamReader(s));
		}
		public String nextLine() throws IOException
		{
			return br.readLine();
		}
		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 double nextDouble() throws IOException
		{
			return Double.parseDouble(next());
		}
		public boolean ready() throws IOException
		{
			return br.ready();
		}
		public long nextLong() throws IOException
		{
			return Long.parseLong(next());
		}
	}
}
