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.util.*;
import java.lang.Math;

public class Main{
	static BufferedReader reader;
	static StringTokenizer tokenizer;
	static PrintWriter writer;

	static int nextInt() throws IOException {
		return Integer.parseInt(nextToken());
	}

	static long nextLong() throws IOException {
		return Long.parseLong(nextToken());
	}

	static double nextDouble() throws IOException {
		return Double.parseDouble(nextToken());
	}

	static String nextToken() throws IOException {
		while (tokenizer == null || !tokenizer.hasMoreTokens()) {
			tokenizer = new StringTokenizer(reader.readLine());
		}
		return tokenizer.nextToken();
	}
	static String nexts() throws IOException {
	  	  tokenizer = new StringTokenizer(reader.readLine());
	   	 String s="";
	   	 while (tokenizer.hasMoreTokens()) {
			s+=tokenizer.nextElement()+" ";
		}
		return s;
	}
	public static int gcd(int x, int y){
		if (y == 0) return x; else return gcd(y, x % y);
	}

	public static boolean isPrime(int nn) 
	    { 
	         if(nn<=1){
		 return false; }
	        if(nn<=3){
		 return true; }
	      if (nn%2==0||nn%3==0){
		 return false; }
	        for (int i=5;i*i<=nn;i=i+6){ 
	            if(nn%i==0||nn%(i+2)==0){
	            	return false;  }
	            }
	         return true; 
	    } 

	public static void shuffle(int[] A) {
		for (int i = 0; i < A.length; i++) {
			int j = (int)(i * Math.random());
			int tmp = A[i];
			A[i] = A[j];
			A[j] = tmp;
		}
	}
	public static void shufflel(Long[] A) {
		for (int i = 0; i < A.length; i++) {
			int j = (int)(i * Math.random());
			long tmp = A[i];
			A[i] = A[j];
			A[j] = tmp;
		}
	}

	public static String reverse(String input)
 	   {
	        StringBuilder input2=new StringBuilder();
	        input2.append(input);
	        input2 = input2.reverse();
	        return input2.toString();
	    }


	 public static long power(int x, long n)
	{
	//    long mod = 1000000007;
		if (n == 0) {
			return 1;
		}

		long pow = power(x, n / 2);

		if ((n & 1) == 1) {
			return (x * pow * pow);
		}
		return (pow * pow);
	}
	public static long power(long x, long y, long p)     //x^y%p
	    { 
  	       long res = 1; 
	       x = x % p; 
  	       while (y > 0) { 
 	 	 if (y % 2 == 1) {
      	        	        res = (res * x) % p; 
		 }
  		 y = y >> 1; // y = y/2 
     	     	 x = (x * x) % p; 
     	         } 
  	         return res; 
    	} 

	 static long ncr(int n, int k)  
   	 { 
           		 long res = 1; 
  		   // Since C(n, k) = C(n, n-k)  
 		       if (k > n - k) { 
     		       k = n - k; 
      		  } 
  		  // Calculate value of [n*(n-1)*---*(n-k+1)] / [k*(k-1)*---*1]  
     		   for (int i = 0; i < k; ++i) { 
        		    res *= (n - i); 
         		   res /= (i + 1); 
     		   } 
  		  return res; 
 	   }
	public static int inv(int a, int m)     //Returns modulo inverse of a with respect to m using extended euclid algorithm
	    { 
	        int m0=m,t,q; 
	        int x0=0,x1=1; 
      	        if(m==1){
	                return 0; }
                 	         while(a>1) 
     	        {  
   	                q=a/m; 
    	                t=m; 
                                 m=a%m;a=t; 
    	                t=x0; 
     	                x0=x1-q*x0; 
      	                x1=t; } 
    	          if(x1<0){
 	   	 x1+=m0; }
   	           return x1; 
	    } 

	static int modInverse(int n, int p) 
  	{ 
    	          return (int)power((long)n, (long)(p - 2),(long)p); 
	 } 
	static int ncrmod(int n, int r, int p) 
   	 { 
	        if (r == 0)        // Base case 
	            return 1; 
  	        int[] fac = new int[n + 1];         // Fill factorial array so that we can find all factorial of r, n and n-r 
	        fac[0] = 1; 
	        for (int i = 1; i <= n; i++) 
                                     fac[i] = fac[i - 1] * i % p; 
   	         return (fac[n] * modInverse(fac[r], p) % p * modInverse(fac[n - r], p) % p) % p;     //IMPORTANT
    	}	 

	static int upper(int a[], int x)   //Returns rightest index of x in sorted arr else -1
  	  {                                                //If not present returns index of just smaller element
  	            int n=a.length;
    	        int l=0;
                int r=n-1;
                int ans=-1;
                while(l<=r){
                    int m=(r-l)/2+l;
                    if(a[m]<=x){
                        ans=m;
                        l=m+1;
                    }
                    else{
                        r=m-1;
                    }
                }
                 return ans;  
                } 
	static int lower(int a[], int x)     //Returns leftest index of x in sorted arr else n
 	   {                                                  //If not present returns index of just greater element
 	            int n=a.length;
   	            int l=0;
                int r=n-1;
                int ans=n;
                while(l<=r){
                    int m=(r-l)/2+l;
                    if(a[m]>=x){
                        ans=m;
                        r=m-1;
                    }
                    else{
                         l=m+1;
                    }
                }
                 return ans; 
                 } 

	public static long stringtoint(String s){ // Convert bit string to number
		long a = 1;
		long ans = 0;
		StringBuilder sb = new StringBuilder();
		sb.append(s);  
		sb.reverse();
		s=sb.toString();
		for(int i=0;i<s.length();i++){
			ans = ans + a*(s.charAt(i)-'0');
			a = a*2;
		}
		return ans;
	}
 
	String inttostring(long a,long m){        // a is number and m is length of string required
		String res = "";                     // Convert a number in bit string representation
		for(int i=0;i<(int)m;i++){
			if((a&(1<<i))==1){
				res+='1';
			}else
				res+='0';
		}
		StringBuilder sb = new StringBuilder();
		sb.append(res);  
		sb.reverse();
		res=sb.toString();
		return res;
    }
	
	 static class R implements Comparable<R>{
	        int x, y;
	        public  R(int x, int y) {           //a[i]=new R(x,y);
	            this.x = x;
	            this.y = y;
	        }
	        public int compareTo(R o) {
            		return x-o.x;     //Increasing order(Which is usually required)
        		}
	    }   
/*   FUNCTION TO SORT HASHMAP ACCORDING TO VALUE
//USE IT AS FOLLOW	

//Make a new list
List<Map.Entry<Integer, Integer> > list = 
               new LinkedList<Map.Entry<Integer, Integer> >(h.entrySet()); 
  
        // Sort the list 
        Collections.sort(list, new Comparator<Map.Entry<Integer, Integer> >() { 
            public int compare(Map.Entry<Integer, Integer> o1,  
                               Map.Entry<Integer, Integer> o2) 
            { 
                return (o1.getValue()).compareTo(o2.getValue());     //This is used to sort string stored as VALUE, use below function here accordingly
            } 
        }); 
          
        // put data from sorted list to new hashmap  
        HashMap<String, Integer> temp = new LinkedHashMap<String, Integer>(); 
        for (Map.Entry<String, Integer> aa : list) { 
            temp.put(aa.getKey(), aa.getValue()); 
        } 
        return temp;   //Now temp is our new sorted hashmap
OR
	for(int i = 0;i<h.size();i++)  //accessing elements from the list made
		{
			int count = list.get(i).getValue();    //Value
			while(count >= 0)
			{
					int key=list.get(i).getKey();  //key
					count -- ;
			}
		}

////////////////////////////////////////////////////////////////////////////////////////
public int compare(Entry<Integer, Integer> o1, Entry<Integer, Integer> o2) 
	{
		if(o1.getValue() != o2.getValue())
			return o1.getValue() > o2.getValue()?1:-1;  //Sorts Value in increasing order
		else if(o1.getValue() == o2.getValue()){
			return o1.getKey() > o2.getKey() ? 1:-1;  //If value equal, then sorts key in increasing order
		}
		
		return Integer.MIN_VALUE;
	}
*/
//Check if palindrome string - System.out.print(A.equals(new StringBuilder(A).reverse().toString())?"Yes":"No");
	public static void main(String[] args) throws IOException {
		reader = new BufferedReader(new InputStreamReader(System.in));
		tokenizer = null;
		writer = new PrintWriter(System.out);
		solve();
		reader.close();
		writer.close();
	}
	
	private static void solve() throws IOException {
	//	int t = nextInt();
	//	while(t-->0){
			//String s= nextToken();
			//String[] s = str.split("\\s+");
			ArrayList<Integer> ar=new ArrayList<Integer>();
			//HashSet<Integer> set=new HashSet<Integer>();
			//HashMap<Integer,String> h=new HashMap<Integer,String>();
			//R[] a1=new R[n];
			
			//PriorityQueue<Integer> pq=new PriorityQueue<Integer>(Collections.reverseOrder());
			//NavigableSet<Integer> pq=new TreeSet<>();
			int n = nextInt();
			//long n = nextLong();
            char[] c=nextToken().toCharArray();
			//int[] a=new int[n];
			//long[] a=new long[n];
			int k=0;
			for(int i=0;i<n-1;i++){
			    if(c[i]!=c[i+1])k=1;
			}
			if(k==0){
			    writer.println(0);
			    return;
			}
			int u=0;
			int co=0;
			char[] cc=new char[n];
			for(int i=0;i<n;i++){
			    cc[i]=c[i];
			}
			
			for(int i=0;i<n-1;i++){
				if(c[i]=='W'){
				    ar.add(i+1);
				    co++;
				    c[i]='B';
				    c[i+1]=c[i+1]=='W'?'B':'W';
				}
			}
			for(int i=0;i<n;i++)if(c[i]=='W')u=1;
			if(u==0){
			    writer.println(co);
			    for(int p:ar)writer.print(p+" ");
			    return;
			}
			co=0;
			u=0;
		    ArrayList<Integer> a=new ArrayList<Integer>();
			for(int i=0;i<n-1;i++){
				if(cc[i]=='B'){
				    a.add(i+1);
				    co++;
				    cc[i]='W';   
				    cc[i+1]=cc[i+1]=='W'?'B':'W';
				}
			}
			for(int i=0;i<n;i++)if(cc[i]=='B')u=1;
			if(u==0){
			    writer.println(co);
			    for(int p:a)writer.print(p+" ");
			    return;
			}
            writer.println(-1);
            
			
		 }
//	}
}