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 {

	static int INF = 1000000007;

	public static void main(String[] args) {
		// int test = fs.nextInt();
		int test = 1;
		for (int cases = 0; cases < test; cases++) {
			int n = fs.nextInt();
			char ar[] = fs.next().toCharArray();
			int b = 0, w = 0;
			for (int i = 0; i < ar.length; i++) {
				if (ar[i] == 'B') {
					++b;
				} else {
					++w;
				}
			}
			if (b == 0 || w == 0) {
				System.out.println(0);
			} else {
				// w
				ArrayList<Integer> al1 = new ArrayList<Integer>();
				ArrayList<Integer> al2 = new ArrayList<>();
				char ar2[] = Arrays.copyOf(ar, n);
				for (int i = 0; i < n - 1; i++) {
					if (ar[i] == 'W') {
						continue;
					} else {
						ar[i] = 'W';
						ar[i + 1] = ar[i + 1] == 'W' ? 'B' : 'W';
						al1.add(i + 1);
					}
				}
				for (int i = 0; i < n - 1; i++) {
					if (ar2[i] == 'B') {
						continue;
					} else {
						ar2[i] = 'B';
						ar2[i + 1] = ar2[i + 1] == 'B' ? 'W' : 'B';
						al2.add(i + 1);
					}
				}
				if (ar[n - 1] != ar[n - 2] && ar2[n - 1] != ar2[n - 2]) {
					System.out.println(-1);
				} else if (ar[n - 1] == ar[n - 2] && ar2[n - 1] == ar2[n - 2]) {
					int min = Integer.min(al1.size(), al2.size());
					if (min > 3 * n) {
						System.out.println(-1);
					} else {
						if (min == al1.size()) {
							System.out.println(al1.size());
							for (Integer integer : al1) {
								System.out.print(integer + " ");
							}
						} else {
							System.out.println(al2.size());
							for (Integer integer : al2) {
								System.out.print(integer + " ");
							}
						}
					}
				} else if (ar[n - 1] == ar[n - 2]) {
					if (al1.size() > 3 * n) {
						System.out.println(-1);
					} else {
						System.out.println(al1.size());
						for (Integer integer : al1) {
							System.out.print(integer + " ");
						}
					}
				} else {
					if (al2.size() > 3 * n) {
						System.out.println(-1);
					} else {
						System.out.println(al2.size());
						for (Integer integer : al2) {
							System.out.print(integer + " ");
						}
					}
				}
			}

		}
	}

	static long power(long x, long y, long p) {
		long res = 1;
		x = x % p;
		while (y > 0) {
			if (y % 2 == 1)
				res = (res * x) % p;
			y = y >> 1;
			x = (x * x) % p;
		}
		return res;
	}

	static long modInverse(long n, long p) {
		return power(n, p - 2, p);
	}

	static long nCrModPFermat(long n, long r, long p) {
		long ans1 = 1;
		long i = n;
		long k = r;
		while (k > 0) {
			ans1 = mul(ans1, i, p);
			i--;
			k--;
		}
		long ans2 = 1;
		while (r > 0) {
			ans2 = mul(ans2, r, p);
			r--;
		}
		r = modInverse(ans2, p);
		ans1 = mul(ans1, r, p);
		return ans1;
	}

	static long facCalc(long total) {
		long ans = 1;
		for (long i = 2; i <= total; i++) {
			ans = mul(ans, i, INF);
		}
		return ans;
	}

	static long mul(long a, long b, long p) {
		return ((a % p) * (b % p)) % p;
	}

	static void sieve() {
		boolean prime[] = new boolean[101];
		Arrays.fill(prime, true);
		prime[1] = false;
		for (int i = 2; i * i <= prime.length - 1; i++) {
			for (int j = i * i; j <= prime.length - 1; j += i) {
				prime[j] = false;
			}
		}
	}

	public static int[] radixSort(int[] f) {
		return radixSort(f, f.length);
	}

	public static int[] radixSort(int[] f, int n) {
		int[] to = new int[n];
		{
			int[] b = new int[65537];
			for (int i = 0; i < n; i++)
				b[1 + (f[i] & 0xffff)]++;
			for (int i = 1; i <= 65536; i++)
				b[i] += b[i - 1];
			for (int i = 0; i < n; i++)
				to[b[f[i] & 0xffff]++] = f[i];
			int[] d = f;
			f = to;
			to = d;
		}
		{
			int[] b = new int[65537];
			for (int i = 0; i < n; i++)
				b[1 + (f[i] >>> 16)]++;
			for (int i = 1; i <= 65536; i++)
				b[i] += b[i - 1];
			for (int i = 0; i < n; i++)
				to[b[f[i] >>> 16]++] = f[i];
			int[] d = f;
			f = to;
			to = d;
		}
		return f;
	}

	static void printArray(int ar[]) {
		System.out.println(Arrays.toString(ar));
	}

	static class Pair {
		int first, second;

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

	}

	static class Pair2 {
		int first;
		Pair second;

		public Pair2(int first, Pair second) {
			this.first = first;
			this.second = second;
		}

	}

	static class LongPair {
		long first, second;

		public LongPair(long first, long second) {
			this.first = first;
			this.second = second;
		}

	}

	static long expmodulo(long a, long b, long c) {
		long x = 1;
		long y = a;
		while (b > 0) {
			if (b % 2 == 1) {
				x = (x * y) % c;
			}
			y = (y * y) % c; // squaring the base
			b /= 2;
		}
		return (long) x % c;
	}

	// static int modInverse(int a, int m) {
	// int m0 = m;
	// int y = 0, x = 1;
	//
	// if (m == 1)
	// return 0;
	//
	// while (a > 1) {
	// int q = a / m;
	// int t = m;
	// m = a % m;
	// a = t;
	// t = y;
	// y = x - q * y;
	// x = t;
	// }
	// if (x < 0)
	// x += m0;
	// return x;
	// }

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

	static void sortMyMapusingValues(HashMap<String, Integer> hm) {

		List<Map.Entry<String, Integer>> capitalList = new LinkedList<>(hm.entrySet());

		Collections.sort(capitalList, new Comparator<Map.Entry<String, Integer>>() {
			public int compare(Map.Entry<String, Integer> o1, Map.Entry<String, Integer> o2) {
				return (o1.getValue()).compareTo(o2.getValue());
			}
		});
		HashMap<String, Integer> result = new HashMap<>();
		for (Map.Entry<String, Integer> entry : capitalList) {
			result.put(entry.getKey(), entry.getValue());
		}
	}

	static boolean ispowerof2(long num) {
		if ((num & (num - 1)) == 0)
			return true;
		return false;
	}

	static void primeFactors(int n) {
		while (n % 2 == 0) {
			System.out.print(2 + " ");
			n /= 2;
		}
		for (int i = 3; i <= Math.sqrt(n); i += 2) {
			while (n % i == 0) {
				System.out.print(i + " ");
				n /= i;
			}
		}
		if (n > 2)
			System.out.print(n);
	}

	static boolean isPrime(long n) {
		// Corner cases
		if (n <= 1)
			return false;
		if (n <= 3)
			return true;
		if (n % 2 == 0 || n % 3 == 0)
			return false;

		long sq = (long) Math.sqrt(n);
		for (int i = 5; i <= sq; i = i + 6)
			if (n % i == 0 || n % (i + 2) == 0)
				return false;

		return true;
	}

	static class Graph {
		HashMap<Integer, LinkedList<Integer>> hm = new HashMap<Integer, LinkedList<Integer>>();

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

		private void addEdge(int source, int 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 uniCycle(int i, HashSet<Integer> visited, int parent) {
			visited.add(i);
			LinkedList<Integer> list = hm.get(i);
			Iterator<Integer> it = list.iterator();
			while (it.hasNext()) {
				Integer integer = (Integer) it.next();
				if (!visited.contains(integer)) {
					if (uniCycle(integer, visited, i))
						return true;
				} else if (integer != parent) {
					return true;
				}
			}
			return false;
		}

		private boolean uniCyclic() {
			HashSet<Integer> visited = new HashSet<Integer>();
			Set<Integer> set = hm.keySet();
			for (Integer integer : set) {
				if (!visited.contains(integer)) {
					if (uniCycle(integer, visited, -1)) {
						return true;
					}
				}
			}
			return false;
		}

		private boolean isbiCycle(int i, HashSet<Integer> visited, HashSet<Integer> countered) {
			if (countered.contains(i))
				return true;
			if (visited.contains(i))
				return false;
			visited.add(i);
			countered.add(i);
			LinkedList<Integer> list = hm.get(i);
			Iterator<Integer> it = list.iterator();
			while (it.hasNext()) {
				Integer integer = (Integer) it.next();
				if (isbiCycle(integer, visited, countered)) {
					return true;
				}
			}
			countered.remove(i);
			return false;
		}

		Boolean isReachable(int s, int d, int k) {
			if (hm.isEmpty()) {
				return false;
			}
			LinkedList<Integer> temp;
			boolean visited[] = new boolean[k];
			LinkedList<Integer> queue = new LinkedList<Integer>();
			visited[s] = true;
			queue.add(s);
			Iterator<Integer> i;
			while (queue.size() != 0) {
				s = queue.poll();
				int n;
				i = hm.get(s).listIterator();

				// Get all adjacent vertices of the dequeued vertex s
				// If a adjacent has not been visited, then mark it
				// visited and enqueue it
				while (i.hasNext()) {
					n = i.next();

					// If this adjacent node is the destination node,
					// then return true
					if (n == d)
						return true;

					// Else, continue to do BFS
					if (!visited[n]) {
						visited[n] = true;
						queue.add(n);
					}
				}
			}

			// If BFS is complete without visited d
			return false;
		}

		private boolean isbiCyclic() {
			HashSet<Integer> visited = new HashSet<Integer>();
			HashSet<Integer> countered = new HashSet<Integer>();
			Set<Integer> set = hm.keySet();
			for (Integer integer : set) {
				if (isbiCycle(integer, visited, countered)) {
					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 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 FastReader fs = new FastReader();
	private static final OutputWriter op = new OutputWriter(System.out);
}