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.util.*;
import java.lang.*;
import java.io.*;

public class ATwistyMovement {

    public static void main(String args[]) throws IOException {
        FastReader in = new FastReader();
        OutputStream outputStream = System.out;
        PrintWriter out = new PrintWriter(outputStream);
        Task.solve(in, out);
        out.close();
    }

    static class Task {

        public static void solve(FastReader in, PrintWriter out) {
            int n = in.nextInt();
            int[] a = new int[n];
            int[] o = new int[n];
            int[] t = new int[n];
            for(int i=0;i<n;i++){
                a[i] = in.nextInt();
                if(i==0){
                    if(a[i]==1){
                        o[0]=1;
                        t[0]=0;
                    }else{
                        o[0]=0;
                        t[0]=1;
                    }
                }else{
                    if(a[i]==1){
                        o[i] = o[i-1]+1;
                        t[i] = t[i-1];
                    } else {
                        o[i] = o[i-1];
                        t[i] = t[i-1]+1;
                    }
                }
            }
            int ans =0;
            for(int i=1;i<n;i++){
                int v1 = t[i-1], v2=t[n-1]-t[i-1];
                for(int j=0;j<i;j++){
                    if(j==i-1){
                        v1 = Math.max(v1, o[i-1]);
                    }else{
                        v1 = Math.max(o[j]+t[i-1]-t[j],v1);
                    }
                }
                for(int k=i;k<n;k++){
                    v2 = Math.max(v2, o[k]-o[i-1]+t[n-1]-t[k]);
                }
//                System.out.println(i+" "+v1+" "+v2);
                ans = Math.max(ans,v1+v2);
            }
            for(int i=0;i<n;i++){
                ans = Math.max(ans,o[i]+t[n-1]-t[i]);
            }
            ans = Math.max(ans,t[n-1]);
            System.out.println(ans);
        }
    }

    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;
        }
    }
}
