Problem: There are n blocks arranged in a row and numbered from left to right, starting from one. Each block is either black or white. 

You may perform the following operation zero or more times: choose two adjacent blocks and invert their colors (white block becomes black, and vice versa). 

You want to find a sequence of operations, such that they make all the blocks having the same color. You don't have to minimize the number of operations, but it should not exceed 3 ⋅ n. If it is impossible to find such a sequence of operations, you need to report it.

Input

The first line contains one integer n (2 ≤ n ≤ 200) — the number of blocks.

The second line contains one string s consisting of n characters, each character is either "W" or "B". If the i-th character is "W", then the i-th block is white. If the i-th character is "B", then the i-th block is black. 

Output

If it is impossible to make all the blocks having the same color, print -1.

Otherwise, print an integer k (0 ≤ k ≤ 3 ⋅ n) — the number of operations. Then print k integers p_1, p_2, ..., p_k (1 ≤ p_j ≤ n - 1), where p_j is the position of the left block in the pair of blocks that should be affected by the j-th operation.

If there are multiple answers, print any of them.

Examples

Input


8
BWWWWWWB


Output


3
6 2 4


Input


4
BWBB


Output


-1


Input


5
WWWWW


Output


0


Input


3
BWB


Output


2
2 1 

Note

In the first example, it is possible to make all blocks black in 3 operations. Start with changing blocks 6 and 7, so the sequence is "BWWWWBBB". Then change blocks 2 and 3, so the sequence is "BBBWWBB". And finally, change blocks 4 and 5, so all blocks are black.

It is impossible to make all colors equal in the second example.

All blocks are already white in the third example.

In the fourth example it is possible to make all blocks white in two operations: first operation is to change blocks 2 and 3 (so the sequence is "BBW"), and then change blocks 1 and 2 (so all blocks are white).

Solution (in JAVA):

Solution:
import java.io.*;
import java.math.*;
import java.util.*;

public class test {

	public static void main(String[] args) {
//		int test = fs.nextInt();
		int test = 1;
		for (int cases = 0; cases < test; cases++) {
			int n = fs.nextInt();
			String s = fs.next();
			boolean ans1 = false;
			boolean ans2 = false;
			StringBuilder ss = new StringBuilder(s);
			ArrayList<Integer> ops1 = new ArrayList<Integer>();
			ArrayList<Integer> ops2 = new ArrayList<Integer>();

			for (int i = 0; i < ss.length() - 1; i++) {
				if (ss.charAt(i) == 'W') {
					continue;
				} else {
					ss.setCharAt(i, 'W');
					ops1.add(i + 1);
					if (ss.charAt(i + 1) == 'W') {
						ss.setCharAt(i + 1, 'B');
					} else {
						ss.setCharAt(i + 1, 'W');
					}
				}
			}
			if (ss.charAt(n - 1) == 'W') {
				ans1 = true;
			} else {
				StringBuilder sss = new StringBuilder(s);
				for (int i = 0; i < sss.length() - 1; i++) {
					if (sss.charAt(i) == 'B') {
						continue;
					} else {
						sss.setCharAt(i, 'B');
						ops2.add(i + 1);
						if (sss.charAt(i + 1) == 'W') {
							sss.setCharAt(i + 1, 'B');
						} else {
							sss.setCharAt(i + 1, 'W');
						}
					}
				}
				if (sss.charAt(n - 1) == 'B') {
					ans2 = true;
				}
			}
			if (ans1) {
				op.print(ops1.size() + "\n");
				if (!ops1.isEmpty()) {
					for (Integer integer : ops1) {
						op.print(integer + " ");
					}
				}
			} else if (ans2) {
				op.print(ops2.size() + "\n");
				if (!ops2.isEmpty()) {
					for (Integer integer : ops2) {
						op.print(integer + " ");
					}
				}
			} else {
				op.print(-1);
			}
			op.flush();
		}
	}

	/*
	 * array list
	 * 
	 * ArrayList<Integer> al=new ArrayList<>(); creating BigIntegers
	 * 
	 * BigInteger a=new BigInteger(); BigInteger b=new BigInteger();
	 * 
	 * hash map
	 * 
	 * HashMap<Integer,Integer> hm=new HashMap<Integer,Integer>(); for(int
	 * i=0;i<ar.length;i++) { Integer c=hm.get(ar[i]); if(hm.get(ar[i])==null) {
	 * hm.put(ar[i],1); } else { hm.put(ar[i],++c); } }
	 * 
	 * while loop
	 * 
	 * int t=sc.nextInt(); while(t>0) { t--; }
	 * 
	 * array input
	 * 
	 * int n = sc.nextInt(); int ar[] = new int[n]; for (int i = 0; i < ar.length;
	 * i++) { ar[i] = sc.nextInt(); }
	 */
	static class Graph {
		HashMap<Character, LinkedList<Character>> hm = new HashMap<Character, LinkedList<Character>>();

		private void addVertex(char vertex) {
			hm.put(vertex, new LinkedList<>());
		}

		private void addEdge(char source, char dest, boolean bi) {
			if (!hm.containsKey(source))
				addVertex(source);
			if (!hm.containsKey(dest))
				addVertex(dest);
			hm.get(source).add(dest);
			if (bi) {
				hm.get(dest).add(source);
			}
		}

		private boolean isCyclicUtil(char ch, boolean visited[], char parent, HashMap<Character, Integer> index) {
			visited[index.get(ch)] = true;
			Iterator<Character> it = hm.get(ch).iterator();
			while (it.hasNext()) {
				Character character = (Character) it.next();
				if (!visited[index.get(character)]) {
					if (isCyclicUtil(character, visited, ch, index))
						return true;
				} else if (character != ch)
					return true;
			}
			return false;
		}

		private boolean isCyclic(HashMap<Character, Integer> index) {
			boolean visited[] = new boolean[hm.size()];
			Set<Character> set = hm.keySet();
			for (Character character : set) {
				if (!visited[index.get(character)]) {
					if (isCyclicUtil(character, visited, '-', index))
						return true;
				}
			}
			return false;
		}
	}

	static class Node {
		Node left, right;
		int data;

		public Node(int data) {
			this.data = data;
		}

		public void insert(int val) {
			if (val <= data) {
				if (left == null) {
					left = new Node(val);
				} else {
					left.insert(val);
				}
			} else {
				if (right == null) {
					right = new Node(val);
				} else {
					right.insert(val);
				}
			}
		}

		public boolean contains(int val) {
			if (data == val) {
				return true;
			} else if (val < data) {
				if (left == null) {
					return false;
				} else {
					return left.contains(val);
				}
			} else {
				if (right == null) {
					return false;
				} else {
					return right.contains(val);
				}
			}
		}

		public void inorder() {
			if (left != null) {
				left.inorder();
			}
			System.out.print(data + " ");
			if (right != null) {
				right.inorder();
			}
		}

		public int maxDepth() {
			if (left == null)
				return 0;
			if (right == null)
				return 0;
			else {
				int ll = left.maxDepth();
				int rr = right.maxDepth();
				if (ll > rr)
					return (ll + 1);
				else
					return (rr + 1);
			}
		}

		public int countNodes() {
			if (left == null)
				return 1;
			if (right == null)
				return 1;
			else {
				return left.countNodes() + right.countNodes() + 1;
			}
		}

		public void preorder() {
			System.out.print(data + " ");
			if (left != null) {
				left.inorder();
			}

			if (right != null) {
				right.inorder();
			}

		}

		public void postorder() {
			if (left != null) {
				left.inorder();
			}

			if (right != null) {
				right.inorder();
			}
			System.out.print(data + " ");

		}

		public void levelorder(Node node) {
			LinkedList<Node> ll = new LinkedList<Node>();
			ll.add(node);
			getorder(ll);

		}

		public void getorder(LinkedList<Node> ll) {
			while (!ll.isEmpty()) {
				Node node = ll.poll();
				System.out.print(node.data + " ");
				if (node.left != null)
					ll.add(node.left);
				if (node.right != null)
					ll.add(node.right);
			}
		}
	}

	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;
		}
	}

	static class Pair {
		int first, second;

		public Pair(int first, int second) {
			this.first = first;
			this.second = second;
		}

	}

	static class OutputWriter {
		private final PrintWriter writer;

		public OutputWriter(OutputStream outputStream) {
			writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
		}

		public OutputWriter(Writer writer) {
			this.writer = new PrintWriter(writer);
		}

		public void print(Object... objects) {
			for (int i = 0; i < objects.length; i++) {
				if (i != 0)
					writer.print(' ');
				writer.print(objects[i]);
			}
		}

		public void printLine(Object... objects) {
			print(objects);
			writer.println();
		}

		public void close() {
			writer.close();
		}

		public void flush() {
			writer.flush();
		}

	}

	private static final Scanner sc = new Scanner(System.in);
	private static final FastReader fs = new FastReader();
	private static final OutputWriter op = new OutputWriter(System.out);

	static int[] getintarray(int n) {
		int ar[] = new int[n];
		for (int i = 0; i < n; i++) {
			ar[i] = fs.nextInt();
		}
		return ar;
	}

	static long[] getlongarray(int n) {
		long ar[] = new long[n];
		for (int i = 0; i < n; i++) {
			ar[i] = fs.nextLong();
		}
		return ar;
	}

	static int[][] get2darray(int n, int m) {
		int ar[][] = new int[n][m];
		for (int i = 0; i < n; i++) {
			for (int j = 0; j < m; j++) {
				ar[i][j] = fs.nextInt();
			}
		}
		return ar;
	}

	static Pair[] getpairarray(int n) {
		Pair ar[] = new Pair[n];
		for (int i = 0; i < n; i++) {
			ar[i] = new Pair(fs.nextInt(), fs.nextInt());
		}
		return ar;
	}

	static void printarray(int ar[]) {
		for (int i : ar) {
			op.print(i + " ");
		}
		op.flush();
	}

	static int fact(int n) {
		int fact = 1;
		for (int i = 2; i <= n; i++) {
			fact *= i;
		}
		return fact;
	}

//	

	// function to find largest prime factor

}/*
	 * 1 5 -2 -3 -1 -4 -6till here
	 */

//		while (t > 0) {
//			int a[] = getintarray(3);
//			int b[] = getintarray(3);
//			int ans = getans(a, b);
//			System.out.println(ans);
//		}