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.StringTokenizer;

public class main933A {
    public static PrintWriter out = new PrintWriter(System.out);
    public static FastScanner enter = new FastScanner(System.in);

    public static void main(String[] args) throws IOException {
        solve();
        out.close();
    }

    private static void solve() throws IOException {
        int n = enter.nextInt();
        int[] arr = new int[n + 1];
        for (int i = 1; i < n + 1; i++) {
            arr[i] = enter.nextInt();
        }
        int[] dp1=new int[n+1];
        int[] dp2=new int[n+1];
        for (int i = 1; i <n+1 ; i++) {
            dp1[i]=dp1[i-1]+(2-arr[i]);
            dp2[i]=dp2[i-1]+arr[i]/2;
        }
        int ans=0;
        for (int i = 1; i <n+1 ; i++) {
            int maxRight=dp2[n]-dp2[i];
            for (int j = i+1; j <n+1 ; j++) {
                maxRight=Math.max(dp1[j]-dp1[i] + dp2[n]-dp2[j], maxRight);
            }
            int maxLeft=dp2[i-1]-dp2[0];
            for (int j = 1; j <i ; j++) {
                maxLeft=Math.max(dp2[i-1]-dp2[j]+dp1[j]-dp1[0],maxLeft);
            }
            ans=Math.max(ans, maxRight+maxLeft+1);
        }
        out.println(ans);
    }

    static class FastScanner {
        BufferedReader br;
        StringTokenizer stok;

        FastScanner(InputStream is) {
            br = new BufferedReader(new InputStreamReader(is));
        }

        String next() throws IOException {
            while (stok == null || !stok.hasMoreTokens()) {
                String s = br.readLine();
                if (s == null) {
                    return null;
                }
                stok = new StringTokenizer(s);
            }
            return stok.nextToken();
        }

        int nextInt() throws IOException {
            return Integer.parseInt(next());
        }

        long nextLong() throws IOException {
            return Long.parseLong(next());
        }

        double nextDouble() throws IOException {
            return Double.parseDouble(next());
        }

        char nextChar() throws IOException {
            return (char) (br.read());
        }

        String nextLine() throws IOException {
            return br.readLine();
        }
    }
}
