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.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.Writer;
import java.util.Arrays;
import java.util.InputMismatchException;
import java.util.*;
import java.io.*;
import java.math.*;
public class Main7{

static class Pair
    { 
        int x;
		int y;
		public Pair(int x, int y) 
        {     
            this.x=x;
			this.y=y;
		}     
        
    @Override
            public int hashCode() 
            { 
                final int temp = 14; 
                int ans = 1; 
                ans =x*31+y*13; 
                return ans; 
            } 
      
            // Equal objects must produce the same 
            // hash code as long as they are equal 
        @Override
        public boolean equals(Object o) 
        { 
            if (this == o) { 
                return true; 
            } 
            if (o == null) { 
                return false; 
            } 
            if (this.getClass() != o.getClass()) { 
                return false; 
            } 
            Pair other = (Pair)o; 
            if (this.x != other.x || this.y!=other.y) { 
                return false; 
            } 
            return true; 
        } 
            
    } 
static class Pair1{
	int x;
	int y;
	long z;
	Pair1(int x, int y, long z)
	{
		this.x=x;
		this.y=y;
		this.z=z;
	}
}
    
    public static long pow(long a, long b)
    {
        long result=1;
        while(b>0)
        {
            if (b % 2 != 0)
            {
                result=(result*a)%1000000007;
                b--;
            } 
            a=(a*a)%1000000007;
            b /= 2;
        }   
        return result;
    }
    public static long fact(long num)
    {
                long value=1;
                long i=1;
                for(i=2;i<=num;i++)
                {
                    value=((value)*(long)i);
                }
                return value;
            }
            public static long gcd(long a, long b)
            {
                if (a == 0)
                    return b;
                return gcd(b%a, a);
            }
            
    /*        public static long lcm(long a,long b)
            {
                return a * (b / gcd(a, b));
            }
        */    public static long sum(int h)
            {
                return (h*(h+1)/2);
            }
      /*     public static void dfs(int parent,boolean[] visited)
            {
                ArrayList<Integer> arr=new ArrayList<Integer>();
                arr=graph.get(parent);
				ts.add(parent);
                visited[parent]=true;
                for(int i=0;i<arr.size();i++)
                {
                    int num=(int)arr.get(i);
                    if(visited[num]==false)
                    {
                        dfs(num,visited);
                    }
                }
            }
			static ArrayList<Integer> ts;
            static int[] dis;*/
            static int mod=1000000007;
            static ArrayList<ArrayList<Integer>> graph;
            static ArrayList<ArrayList<Integer>> g;
            
       /*    public static void bfs(int num,int size)
            {
                boolean[] visited=new boolean[size+1];
                Queue<Integer> q=new LinkedList<>();
                q.add(num);
                ans[num]=1;
                visited[num]=true;
                while(!q.isEmpty())
                {
                    int x=q.poll();
                    ArrayList<Integer> al=graph.get(x);
                    for(int i=0;i<al.size();i++)
                    {
                        int y=al.get(i);    
                        if(visited[y]==false)
                        {
                            q.add(y);
                            ans[y]=ans[x]+1;
                            visited[y]=true;
                        }
                    }
                }
            }
			
            static int[] ans;*/
			static public void main(String args[])throws IOException
            {
				int t=1;
				StringBuilder sb=new StringBuilder();
				while(t-->0)
				{
					int n=i();
					String s=s();
					char[] ch=s.toCharArray();
					ArrayList<Integer> ar=new ArrayList<>();
					ArrayList<Integer> ar1=new ArrayList<>();
					ArrayList<Integer> ar2=new ArrayList<>();
					for(int i=0;i<n;i++)
					{
						if(ch[i]=='B')
							ar.add(i);
						else
							ar1.add(i);
					}
					if(ar.size()==0 || ar1.size()==0)
					{
						sb.append("0\n");
					}
					else
					{
						for(int i=0;i<n-1;i++)
						{
							if(ch[i]=='W')
							{
								ar2.add(i+1);
								ch[i]='B';
								if(ch[i+1]=='W')
									ch[i+1]='B';
								else
									ch[i+1]='W';
							}
						}
						int cc=0;
						for(int i=0;i<n;i++)
						{
							if(ch[i]=='B')
								cc++;
						}
						if(cc==n)
						{
							sb.append(ar2.size()+"\n");
							for(int i=0;i<ar2.size();i++)
								sb.append(ar2.get(i)+" ");
							sb.append("\n");
						}
						else
						{
							ar2.clear();
							ch=s.toCharArray();
							for(int i=0;i<n-1;i++)
							{
								if(ch[i]=='B')
								{
									ar2.add(i+1);
									ch[i]='W';
									if(ch[i+1]=='W')
										ch[i+1]='B';
									else
										ch[i+1]='W';
								}
							}
							cc=0;
							for(int i=0;i<n;i++)
							{
								if(ch[i]=='W')
									cc++;
							}
							if(cc==n)
							{
								sb.append(ar2.size()+"\n");
								for(int i=0;i<ar2.size();i++)
									sb.append(ar2.get(i)+" ");
								sb.append("\n");
							}
							else
								sb.append("-1\n");
						}
					}
				}
				System.out.print(sb.toString());
			}
			

            /**/
            static InputReader in=new InputReader(System.in);
                static OutputWriter out=new OutputWriter(System.out);
                public static long l()
                {
                    String s=in.String();
                    return Long.parseLong(s);
                }
                public static void pln(String value)
                {
                    System.out.println(value);
                }
                public static int i()
                {
                    return in.Int();
                }
                public static String s()
                {
                    return in.String();
                }
    }
         
         
         
         
         
         
         
         
         
         
         
         
         
         
         
         
         
         
         
         
         
         
        class InputReader {
             
            private InputStream stream;
            private byte[] buf = new byte[1024];
            private int curChar;
            private int numChars;
            private SpaceCharFilter filter;
         
            public InputReader(InputStream stream) {
                this.stream = stream;
            }
         
            public int read() {
                if (numChars== -1)
                    throw new InputMismatchException();
                if (curChar >= numChars) {
                    curChar = 0;
                    try {
                        numChars = stream.read(buf);
                    } catch (IOException e) {
                        throw new InputMismatchException();
                    }
                    if (numChars <= 0)
                        return -1;
                }
                return buf[curChar++];
            }
         
            public int Int() {
                int c = read();
                while (isSpaceChar(c))
                    c = read();
                int sgn = 1;
                if (c == '-') {
                    sgn = -1;
                    c = read();
                }
                int res = 0;
                do {
                    if (c < '0' || c > '9')
                        throw new InputMismatchException();
                    res *= 10;
                    res += c - '0';
                    c = read();
                } while (!isSpaceChar(c));
                return res * sgn;
            }
         
            public String String() {
                int c = read();
                while (isSpaceChar(c))
                    c = read();
                StringBuilder res = new StringBuilder();
                do {
                    res.appendCodePoint(c);
                    c = read();
                } while (!isSpaceChar(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;
            }
         
            public String next() {
                return String();
            }
         
            public interface SpaceCharFilter {
                public boolean isSpaceChar(int ch);
            }
        }
         
        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();
            }
         
            }
         
            class IOUtils {
         
            public static int[] readIntArray(InputReader in, int size) {
                int[] array = new int[size];
                for (int i = 0; i < size; i++)
                    array[i] = in.Int();
                return array;
            }
         
            }