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.FileNotFoundException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.StringTokenizer;

/**
 * Created by trung.pham on 15/2/18.
 */
public class A_Round_462_Div1 {
    public static long MOD = 1000000007;

    public static void main(String[] args) throws FileNotFoundException {
        // PrintWriter out = new PrintWriter(new FileOutputStream(new File(
        // "output.txt")));
        PrintWriter out = new PrintWriter(System.out);
        Scanner in = new Scanner();
        int n = in.nextInt();
        int[][][]dp = new int[2][2][n*n];
        int[][][]rev = new int[2][2][n*n];
        int[]data = new int[n];
        for(int i = 0; i < n; i++){
            data[i] = in.nextInt() - 1;
        }
        for(int i = n- 1; i >= 0; i--){
            dp[data[i]][data[i]][i*n + i] = 1;
            for(int j = i + 1; j < n; j++){
                dp[0][0][i * n + j] = dp[0][0][i*n + j - 1];
                dp[0][1][i * n + j] = dp[0][1][i * n + j - 1];
                dp[1][1][i*n + j] = dp[1][1][i*n + j - 1];
                if(data[j] == 0){
                    dp[0][0][i*n + j] = 1 + dp[0][0][i*n + j - 1];

                }else{
                    if(dp[0][0][i*n + j - 1] > 0){
                        dp[0][1][i*n + j]= Integer.max(1 + dp[0][1][i*n + j], 1 + dp[0][0][i*n + j]);
                    }
                    dp[1][1][i*n + j] = 1 + dp[1][1][i*n + j - 1];
                }
            }
        }

        for(int i = 0; i < n; i++){
            rev[data[i]][data[i]][i*n + i] = 1;
            for(int j = i -1 ; j >= 0; j--){
                rev[0][0][j*n + i] = rev[0][0][(j + 1)*n +i];
                rev[0][1][j*n +i] = rev[0][1][(j + 1)*n +i];
                rev[1][1][j*n +i] = rev[1][1][(j + 1)*n +i];
                if(data[j] == 0){
                    rev[0][0][j *n +i] = 1 + rev[0][0][(j + 1)*n +i];
                }else{
                    if(rev[0][0][(j + 1)*n +i] != 0){
                        rev[0][1][j*n + i] = Integer.max(1 + rev[0][1][(j + 1)*n +i], 1 + rev[0][0][(j + 1)*n +i]);
                    }
                    rev[1][1][j*n + i] = 1 + rev[1][1][(j + 1)*n +i];
                }
            }
        }

        int re = Integer.max(dp[0][0][n - 1], Integer.max(dp[0][1][n - 1], dp[1][1][n - 1]));
        for(int i = 0; i < n; i++){
            for(int j = i; j < n; j++){
                for(int a = 0;a < 2; a++){
                    for(int b = a; b < 2; b++){
                        for(int c = b; c < 2; c++){
                            for(int d = c ; d < 2; d++) {
                                int tmp = (i != 0 ? dp[a][b][i - 1] : 0) + rev[b][c][i*n + j] + (j + 1 < n ? dp[c][d][(j + 1)*n + n - 1] : 0);
                                re = Integer.max(tmp, re);
                            }
                        }
                    }
                }
            }
        }
        out.println(re);
        out.close();
    }



    public static int[] KMP(String val) {
        int i = 0;
        int j = -1;
        int[] result = new int[val.length() + 1];
        result[0] = -1;
        while (i < val.length()) {
            while (j >= 0 && val.charAt(j) != val.charAt(i)) {
                j = result[j];
            }
            j++;
            i++;
            result[i] = j;
        }
        return result;

    }

    public static boolean nextPer(int[] data) {
        int i = data.length - 1;
        while (i > 0 && data[i] < data[i - 1]) {
            i--;
        }
        if (i == 0) {
            return false;
        }
        int j = data.length - 1;
        while (data[j] < data[i - 1]) {
            j--;
        }
        int temp = data[i - 1];
        data[i - 1] = data[j];
        data[j] = temp;
        Arrays.sort(data, i, data.length);
        return true;
    }

    public static int digit(long n) {
        int result = 0;
        while (n > 0) {
            n /= 10;
            result++;
        }
        return result;
    }

    public static double dist(long a, long b, long x, long y) {
        double val = (b - a) * (b - a) + (x - y) * (x - y);
        val = Math.sqrt(val);
        double other = x * x + a * a;
        other = Math.sqrt(other);
        return val + other;

    }

    public static class Point implements Comparable<Point> {

        int x, y;

        public Point(int start, int end) {
            this.x = start;
            this.y = end;
        }

        @Override
        public int hashCode() {
            int hash = 5;
            hash = 47 * hash + this.x;
            hash = 47 * hash + this.y;
            return hash;
        }

        @Override
        public boolean equals(Object obj) {
            if (obj == null) {
                return false;
            }
            if (getClass() != obj.getClass()) {
                return false;
            }
            final Point other = (Point) obj;
            if (this.x != other.x) {
                return false;
            }
            if (this.y != other.y) {
                return false;
            }
            return true;
        }

        @Override
        public int compareTo(Point o) {
            return Integer.compare(x, o.x);
        }
    }

    public static class FT {

        long[] data;

        FT(int n) {
            data = new long[n];
        }

        public void update(int index, long value) {
            while (index < data.length) {
                data[index] += value;
                index += (index & (-index));
            }
        }

        public long get(int index) {
            long result = 0;
            while (index > 0) {
                result += data[index];
                index -= (index & (-index));
            }
            return result;

        }
    }

    public static long gcd(long a, long b) {
        if (b == 0) {
            return a;
        }
        return gcd(b, a % b);
    }

    public static long pow(long a, long b, long MOD) {
        if (b == 0) {
            return 1;
        }
        if (b == 1) {
            return a;
        }
        long val = pow(a, b / 2, MOD);
        if (b % 2 == 0) {
            return val * val % MOD;
        } else {
            return val * (val * a % MOD) % MOD;

        }
    }

    static class Scanner {

        BufferedReader br;
        StringTokenizer st;

        public Scanner() throws FileNotFoundException {
            // System.setOut(new PrintStream(new BufferedOutputStream(System.out), true));
            br = new BufferedReader(new InputStreamReader(System.in));
            //  br = new BufferedReader(new InputStreamReader(new FileInputStream(new File("input.txt"))));
        }

        public String next() {

            while (st == null || !st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (Exception e) {
                    throw new RuntimeException();
                }
            }
            return st.nextToken();
        }

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

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

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

        public String nextLine() {
            st = null;
            try {
                return br.readLine();
            } catch (Exception e) {
                throw new RuntimeException();
            }
        }

        public boolean endLine() {
            try {
                String next = br.readLine();
                while (next != null && next.trim().isEmpty()) {
                    next = br.readLine();
                }
                if (next == null) {
                    return true;
                }
                st = new StringTokenizer(next);
                return st.hasMoreTokens();
            } catch (Exception e) {
                throw new RuntimeException();
            }
        }
    }
}
