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

public class C {

	public static void main(String[] args){
		FastScanner scan = new FastScanner();	
		PrintWriter out = new PrintWriter(System.out);
		n = scan.nextInt();
		a = scan.nextIntArray(n);
		dp = new Integer[3][4][n];
		out.println(go(0, 0, 0));
		out.close();
	}
	
	static int n, a[];
	static Integer[][][] dp;
	
	static int go(int l, int p, int at) {
		if(at == n) return 0;
		if(dp[l][p][at] != null) return dp[l][p][at];
		int res = 0;
		if(p == 0) {
			res = Math.max(res, go(l, p, at+1));
			res = Math.max(res, go(a[at], p+1, at+1)+1);
		}
		if(p == 1) {
			res = Math.max(res, go(l, p, at+1));
			if(l <= a[at]) res = Math.max(res, go(a[at], p, at+1)+1);
			res = Math.max(res, go(l, p+1, at));
		}
		if(p == 2){
			res = Math.max(res, go(l, p, at+1));
			if(l >= a[at]) res = Math.max(res, go(a[at], p, at+1)+1);
			res = Math.max(res, go(l, p+1, at));
		}
		if(p == 3) {
			res = Math.max(res, go(l, p, at+1));
			if(l <= a[at]) res = Math.max(res, go(a[at], p, at+1)+1);
		}
		return dp[l][p][at] = res;
	}

	static class FastScanner {
		BufferedReader br;
		StringTokenizer st;

		public FastScanner() {
			try	{
				br = new BufferedReader(new InputStreamReader(System.in));
				st = new StringTokenizer(br.readLine());
			} catch (Exception e){e.printStackTrace();}
		}

		public String next() {
			if (st.hasMoreTokens())	return st.nextToken();
			try {st = new StringTokenizer(br.readLine());}
			catch (Exception e) {e.printStackTrace();}
			return st.nextToken();
		}

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

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

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

		public String nextLine() {
			String line = "";
			if(st.hasMoreTokens()) line = st.nextToken();
			else try {return br.readLine();}catch(IOException e){e.printStackTrace();}
			while(st.hasMoreTokens()) line += " "+st.nextToken();
			return line;
		}

		public int[] nextIntArray(int n) {
			int[] a = new int[n];
			for(int i = 0; i < n; i++) a[i] = nextInt();
			return a;
		}

		public long[] nextLongArray(int n){
			long[] a = new long[n];
			for(int i = 0; i < n; i++) a[i] = nextLong();
			return a;
		}

		public double[] nextDoubleArray(int n){
			double[] a = new double[n];
			for(int i = 0; i < n; i++) a[i] = nextDouble();
			return a;
		}

		public char[][] nextGrid(int n, int m){
			char[][] grid = new char[n][m];
			for(int i = 0; i < n; i++) grid[i] = next().toCharArray();
			return grid;
		}
	}


}