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.util.Scanner;
import java.util.Random;
import java.util.Arrays;
public class delete{
    public static void main(String args[]){
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        if(n==1){
            System.out.println("1");
            return;
        }
        int arr[] = new int[n];
        for(int i=0;i<n;i++){
            arr[i] = in.nextInt();
        }
        int dp1[][] = new int[n][n];
        int dp2[][] = new int[n][n];
        int d1[][] = new int[n][n];
        int d2[][] = new int[n][n];
        int c1[] = new int[n];
        int c2[] = new int[n];
        if(arr[0]==1)
            c1[0]++;
        else
            c2[0]++;
        for(int i=1;i<n;i++){
            if(arr[i]==1){
                c1[i] = c1[i-1]+1;
                c2[i] = c2[i-1];
            }
            else{
                c2[i] = c2[i-1]+1;
                c1[i] = c1[i-1];
            }
        }
        for(int i=0;i<n;i++){
            if(arr[i]==1){
                dp1[i][i] = 1;
                d1[i][i] = 1;
            }
            else{
                dp2[i][i] = 1;
                d2[i][i] = 1;
            }
        }
         
        for(int i=0;i<n;i++){
            for(int j=i+1;j<n;j++){
                if(arr[j]==1){
                    dp2[i][j] = dp2[i][j-1];
                    dp1[i][j] = dp1[i][j-1]+1;
                }
                else{
                    dp1[i][j] = dp1[i][j-1];
                    dp2[i][j] = Math.max(dp1[i][j-1],dp2[i][j-1])+1;
                }
            }
        }     
//        for(int i=0;i<n;i++){
//                System.out.println(Arrays.toString(dp1[i]));
//        }
//                for(int i=0;i<n;i++){
//                System.out.println(Arrays.toString(dp2[i]));
//        }
        for(int i=0;i<n;i++){
            for(int j=i+1;j<n;j++){
                if(arr[j]==2){
                    d2[i][j] = d2[i][j-1]+1;
                    d1[i][j] = d1[i][j-1];
                }
                else{
                    d2[i][j] = d2[i][j-1];
                    d1[i][j] = Math.max(d1[i][j-1],d2[i][j-1])+1;
                }
            }
        }
                               
        int max = Integer.MIN_VALUE;
        for(int i=0;i<n;i++)
            for(int j=i+1;j<n;j++)
                max = Math.max(max,Math.max(dp1[i][j],dp2[i][j]));
            
//        System.out.println(max);
        for(int i=0;i<n;i++){
            for(int j=i+1;j<n;j++){
                int a = c1[i] + Math.max(d1[i][j],d2[i][j]) + c2[n-1]-c2[j];
                if(arr[i]==1)
                    a--;
                if(a>max)
                    max = a;
            }
        }
        System.out.println(max);
    }
    
}