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.util.*;
import java.io.*;
public class Codeforces
{
    static InputReader in=new InputReader(System.in);
    static OutputWriter out=new OutputWriter(System.out);    
    static StringBuilder sb=new StringBuilder();
    static long MOD = (long)(998244353);    
    // Main Class Starts Here    
    
    public static void main(String args[])throws IOException
    {
    	// Write your code.    	
    	int t=1;
    	while(t-->0) {
    		int n=in();  
    		char a[]=sn().toCharArray();
    		char x = a[0];
    		Vector<Integer> v=new Vector<>();
    		int count = 0 ;
    		for(int i=1;i<n-1;i++) {
    			if(a[i] == x)
    				continue;
    			v.add(i+1);
    			a[i] = x;
    			if(a[i+1] == 'B')
    				a[i+1] = 'W';
    			else
    				a[i+1] = 'B';
    			count++;
    		}
    		if(a[n-1] != x) {
    			if((n-1) % 2 != 0)app(-1+"\n");
    			else {
    				x = a[n-1];
    				for(int i=0;i<n-1;i+=2) {
    					a[i] = x;
    					a[i+1] = x;
    					count++;
    					v.add(i+1);
    				}
    				app(count+"\n");
    				for(int xx:v)app(xx+" ");
    			}
    		}
    		else {
    			app(count+"\n");
    			for(int xx:v)app(xx+" ");
    		}
       	}    	    	      	
    	out.printLine(sb);
    	out.close();
    }         
               
    static class Pair
    {
    	int x;
    	int y;
    	public Pair(int x,int y) {
    		this.x=x;
    		this.y=y;
    	}
    }
    
    public static long rev(long n) {
    	if(n<10L)
    		return n;
    	long rev = 0L;
    	while(n != 0L) {
    		long a = n % 10L;
    		rev = a + rev*10L;
    		n /= 10L;
    	}
    	return rev;
    }
    
    public static long pow(long a,long b) {
    	if(b==0)
    		return 1L;
    	if(b==1)
    		return a % MOD;
    	long f = a * a;
    	if(f > MOD)
    		f %= MOD;
    	long val = pow(f, b/2) % MOD;
    	if(b % 2 == 0)
    		return val;
    	else {
    		long temp = val * (a % MOD);
    		if(temp > MOD)
    			temp = temp % MOD;
    		return temp;
    	}
    }
    
    public static long lcm(long a,long b) {
    	long lcm = (a*b)/gcd(a,b);
    	return lcm;
    }
    
    public static long gcd(long a,long b) {
    	if(b==0)
    		return a;
    	return gcd(b, a%b);
    }
    
    public static int[] an(int n) {
    	int ar[]=new int[n];
    	for(int i=0;i<n;i++)
    		ar[i]=in();
    	return ar;
    }

    public static long[] lan(int n) {
    	long ar[]=new long[n];
    	for(int i=0;i<n;i++)
    		ar[i]=lin();
    	return ar;
    }    
    
    public static String atos(Object ar[]) {
    	return Arrays.toString(ar);
    }
    
    public static int in() {
    	return in.readInt();
    }
    
    public static long lin() {
    	return in.readLong();
    }    
    
    public static String sn() {
    	return in.readString();
    }
    
    public static void prln(Object o) {    	
    	out.printLine(o);
    }
    
    public static void prn(Object o) {    	
    	out.print(o);
    }
    
    public static int getMax(int a[]) {
    	int n = a.length;
    	int max = a[0];
    	for(int i=1; i < n; i++) {
    		max = Math.max(max, a[i]);
    	}
    	return max;
    }
    
    public static int getMin(int a[]) {
    	int n = a.length;
    	int min = a[0];
    	for(int i=1; i < n; i++) {
    		min = Math.min(min, a[i]);
    	}
    	return min;
    }
    
    public static void display(int a[]) {
    	out.printLine(Arrays.toString(a));
    }    
    
    public static HashMap<Integer,Integer> hm(int a[]){
    	HashMap<Integer,Integer> map=new HashMap<>();
    	for(int i=0; i < a.length;i++) {
    		int keep = (int)map.getOrDefault(a[i],0);
    		map.put(a[i],++keep);
    	}
    	return map;
    }
    
    public static void app(Object o) {
    	sb.append(o);
    }
    
    public static long calcManhattanDist(int x1,int y1,int x2,int y2) {
    	long xa = Math.abs(x1-x2);
    	long ya = Math.abs(y1-y2);
    	return (xa+ya);
    }
    
    
    static 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 readInt() {
            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 long readLong() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long 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 readString() {
            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 readString();
        }

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

    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();
        }
    } 
}