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.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.InputMismatchException;
import java.util.Scanner;

public class C {

	public static void main(String[] args) throws Exception {
		// TODO Auto-generated method stub
		InputReader s = new InputReader(System.in);
		PrintWriter p = new PrintWriter(System.out);
		Scanner sc = new Scanner(System.in);
		int n = s.nextInt();
		String str = s.nextLine();
		char[] arr = new char[n];
		arr = str.toCharArray();
		ArrayList<Integer> list = new ArrayList<>();
		int nw = 0, nb = 0;
		for (int i = 0; i < str.length(); i++) {
			if (str.charAt(i) == 'W')
				nw++;
			else {
				nb++;
			}
		}
		if (nb % 2 == 1 && nw % 2 == 1) {
			System.out.println(-1);
			return;
		}
		for (int i = 0; i < str.length(); i++) {
			if (i == str.length() - 2) {
				break;
			}
			if (arr[i] != arr[i + 1]) {
				list.add(i + 2);
				if (arr[i + 1] == 'W') {
					arr[i + 1] = 'B';
					if (arr[i + 2] == 'B') {
						arr[i + 2] = 'W';
					} else {
						arr[i + 2] = 'B';
					}
				}else if(arr[i + 1] == 'B') {
					arr[i + 1] = 'W';
					if (arr[i + 2] == 'B') {
						arr[i + 2] = 'W';
					} else {
						arr[i + 2] = 'B';
					}
				}
			}
		}
		for (int i = str.length() - 1; i >= 0; i--) {
			if (i <= 1) {
				break;
			}
			if (arr[i] != arr[i - 1]) {
				list.add(i - 1);
				if (arr[i - 1] == 'W') {
					arr[i - 1] = 'B';
					if (arr[i - 2] == 'B') {
						arr[i - 2] = 'W';
					} else {
						arr[i - 2] = 'B';
					}
				}else if (arr[i - 1] == 'B') {
					arr[i - 1] = 'W';
					if (arr[i - 2] == 'B') {
						arr[i - 2] = 'W';
					} else {
						arr[i - 2] = 'B';
					}
				}
			}
		}
		for (int i = 0; i < str.length(); i++) {
			if (i == str.length() - 2) {
				break;
			}
			if (arr[i] != arr[i + 1]) {
				list.add(i + 2);
				if (arr[i + 1] == 'W') {
					arr[i + 1] = 'B';
					if (arr[i + 2] == 'B') {
						arr[i + 2] = 'W';
					} else {
						arr[i + 2] = 'B';
					}
				}else if(arr[i + 1] == 'B') {
					arr[i + 1] = 'W';
					if (arr[i + 2] == 'B') {
						arr[i + 2] = 'W';
					} else {
						arr[i + 2] = 'B';
					}
				}
			}
		}
		System.out.println(list.size());
		for (int i = 0; i < list.size(); i++) {
			System.out.print(list.get(i) + " ");
		}
		p.flush();
		p.close();
	}

	public static ArrayList Divisors(long n) {
		ArrayList<Long> div = new ArrayList<>();

		for (long i = 1; i <= Math.sqrt(n); i++) {
			if (n % i == 0) {
				div.add(i);

				if (n / i != i)
					div.add(n / i);
			}
		}
		return div;
	}

	public static int BinarySearch(long[] a, long k) {
		int n = a.length;
		int i = 0, j = n - 1;
		int mid = 0;

		if (k < a[0])
			return 0;
		else if (k >= a[n - 1])
			return n;
		else {
			while (j - i > 1) {
				mid = (i + j) / 2;

				if (k >= a[mid])
					i = mid;
				else
					j = mid;
			}
		}

		return i + 1;
	}

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

	public static long LCM(long a, long b) {
		return (a * b) / GCD(a, b);
	}

	static class pair implements Comparable<pair> {
		Integer x, y;

		pair(int x, int y) {
			this.x = x;
			this.y = y;
		}

		public int compareTo(pair o) {
			int result = x.compareTo(o.x);
			if (result == 0)
				result = y.compareTo(o.y);

			return result;
		}

		public String toString() {
			return x + " " + y;
		}

		public boolean equals(Object o) {
			if (o instanceof pair) {
				pair p = (pair) o;
				return p.x - x == 0 && p.y - y == 0;
			}
			return false;
		}

		public int hashCode() {
			return new Long(x).hashCode() * 31 + new Long(y).hashCode();
		}
	}

	static class InputReader {

		private final InputStream stream;
		private final byte[] buf = new byte[8192];
		private int curChar, snumChars;
		private SpaceCharFilter filter;

		public InputReader(InputStream stream) {
			this.stream = stream;
		}

		public int snext() {
			if (snumChars == -1)
				throw new InputMismatchException();
			if (curChar >= snumChars) {
				curChar = 0;
				try {
					snumChars = stream.read(buf);
				} catch (IOException e) {
					throw new InputMismatchException();
				}
				if (snumChars <= 0)
					return -1;
			}
			return buf[curChar++];
		}

		public int nextInt() {
			int c = snext();
			while (isSpaceChar(c)) {
				c = snext();
			}
			int sgn = 1;
			if (c == '-') {
				sgn = -1;
				c = snext();
			}
			int res = 0;
			do {
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res *= 10;
				res += c - '0';
				c = snext();
			} while (!isSpaceChar(c));
			return res * sgn;
		}

		public long nextLong() {
			int c = snext();
			while (isSpaceChar(c)) {
				c = snext();
			}
			int sgn = 1;
			if (c == '-') {
				sgn = -1;
				c = snext();
			}
			long res = 0;
			do {
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res *= 10;
				res += c - '0';
				c = snext();
			} while (!isSpaceChar(c));
			return res * sgn;
		}

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

		public String readString() {
			int c = snext();
			while (isSpaceChar(c)) {
				c = snext();
			}
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = snext();
			} while (!isSpaceChar(c));
			return res.toString();
		}

		public String nextLine() {
			int c = snext();
			while (isSpaceChar(c))
				c = snext();
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = snext();
			} while (!isEndOfLine(c));
			return res.toString();
		}

		public boolean isSpaceChar(int c) {
			if (filter != null)
				return filter.isSpaceChar(c);
			return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
		}

		private boolean isEndOfLine(int c) {
			return c == '\n' || c == '\r' || c == -1;
		}

		public interface SpaceCharFilter {
			public boolean isSpaceChar(int ch);
		}
	}

	static class CodeX {
		public static void sort(long arr[]) {
			merge_sort(arr, 0, arr.length - 1);
		}

		private static void merge_sort(long A[], long start, long end) {
			if (start < end) {
				long mid = (start + end) / 2;
				merge_sort(A, start, mid);
				merge_sort(A, mid + 1, end);
				merge(A, start, mid, end);
			}

		}

		private static void merge(long A[], long start, long mid, long end) {
			long p = start, q = mid + 1;
			long Arr[] = new long[(int) (end - start + 1)];
			long k = 0;

			for (int i = (int) start; i <= end; i++) {
				if (p > mid)
					Arr[(int) k++] = A[(int) q++];

				else if (q > end)
					Arr[(int) k++] = A[(int) p++];

				else if (A[(int) p] < A[(int) q])
					Arr[(int) k++] = A[(int) p++];

				else
					Arr[(int) k++] = A[(int) q++];
			}
			for (int i = 0; i < k; i++) {
				A[(int) start++] = Arr[i];
			}

		}

	}

}