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:
/*           
                      
                     _.!._
                    /O*@*O\
                   <\@(_)@/>
          ,;,   .--;`     `;--.   ,
          O@O_ /   |d     b|   \ _hnn
          | `/ \   |       |   / \` |
          &&&&  :##;\     /;##;  &&&&
          |  \ / `##/|   |##'  \ /  |
          \   %%%%`</|   |#'`%%%%   /
           '._|_ \   |   |'  / _|_.'
             _/  /   \   \   \  \
            / (\(     '.  '-._&&&&
           (  ()##,    o'--.._`\-)
            '-():`##########'()()()
             /:::::/()`Y`()\:::::\
             \::::( () | () )::::/
              `"""`\().'.()/'"""`


                                                
                              +''''`--''-..`--..__
                             .\ _,/:i--._`:-:+._`.``-._
                            /`.._,,' \   `-.``--:.b....=.
                           |`..__,,..`.    '`.__::i--.-::_
                           )- .....--i'\..      --+`'''-'
                         ,' .'.._,.-'|._-b\
                        /,'<'    V   `i| \\             
                       |/ -|,--.." ,'-. ||\\\      |||||||||
                       ''/ |  O ' |  O '\ \\\\   _/        _\
                      |,','|    , .     | \\\\\\||  |||||  ||
                   ._,:'/ /-\   '^'   -Y"\\     ||  |||||  ||
                  .|/,'| |/':: ':=:' ,'|  |     ||  |||||  ||
                  |+,';' /|_/ \     _/ \b':.\  \'|       ,'
                  ,,:-i''_i' | ``-.Y',. ,|`: | \;- | |_,'
            __   |'| |i:'._ ,'     ,' ,; | |-)-'  __--:b__
           .P|   | |/,'|\  - ._   /  /   _,Y-   ,:/'  `.  `'".._
          ,'|| -','' | ._i._   `':| ,..,'     ,Y;'      \       `- ._
         |||||,..    | \ '-.._ _,' /       _,b-'         `.         '-.
         ||||P..i,  .| '....,-' _,'''''-'''               '    _,..    `\
         +'`   <'/  |`-.....---'                       ._         ,._
          |      |                                    ,'``,:-''''/,--`.
         Y|.b_,,:  |              ||                 ,;,Y'      /     |.
       ,' /'----' .'|   ..       |  |         '"   .`Y'     .,-b_....;;,.
      |+|,'     | | \.,  '      ,'  `:.  _     ,/__`     _=:  _,'``-
     / +,'      | /\_........:.'      '"----:::::'Y  .'.|   |||
     |' '      .'/- \\                          /'|| || |   |||
     |||      /|     \L                        /'|| ||/ |   |||
     `.|    ,'/       .|                      / ,'||/o;/    |||
       `..._,,         |                      |/|   '       |||
         ``-'          |                      |,            |||
                       |          ,.          |             |||
    ,=--------....     |          ""          |             |||
  ,/,'.            i=..+._             ,..    '..;---:::''- | |
  '/|           __....b `-''`---....../.,Y'''''j:.,.._      | `._
  .'      _.Y.-'       `..       ii:,'--------' |     :-+. .| | b\
  |     .=_,.---'''''--...:..--:'  /         _..-----..:=   | | '|\
  |    '-''`'---                  ---'_,,,--''           `,.. |  | \.
   \  .                      ,' _,--''        ::      _,/ |||   |  \
  `::b\`                 _,-i,-'                 ,..---'    ,|:|  | _|
  `'--.:-._      ____,,,;.,'' `--._      ''''''''           |'|' .'  '
       ``'--....Y''-'              `''--..._..____._____...,' |  'o-'
                                               `''''`'''i==_+=_=i__
                                                       ||'''- '    `.
                                                        `-.......-''  
*/

//package cf;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.HashSet;
import java.util.InputMismatchException;
import java.util.List;
import java.util.Set;
import java.util.TreeSet;
public class Three{
    public static class InputReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private InputReader.SpaceCharFilter filter;
        private BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
     
        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 String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            }
            catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
        public int nextInt() {
            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 nextLong() {
            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 double nextDouble() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            double res = 0;
            while (!isSpaceChar(c) && c != '.') {
                if (c == 'e' || c == 'E')
                    return res * Math.pow(10, nextInt());
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            }
            if (c == '.') {
                c = read();
                double m = 1;
                while (!isSpaceChar(c)) {
                    if (c == 'e' || c == 'E')
                        return res * Math.pow(10, nextInt());
                    if (c < '0' || c > '9')
                        throw new InputMismatchException();
                    m /= 10;
                    res += (c - '0') * m;
                    c = read();
                }
            }
            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 long gcd(long a, long b){
        if (a == 0)
            return b;  
        return gcd(b % a, a);  
    }
    static long lcm(long a, long b)  {
        return (a*b)/gcd(a, b);  
    }
    
    // Select a particular column and the entire rows will be shifted and the selected column will be sorted while other columns will be 
    // rearranged accordingly
    public static void sortbyColumn(long arr[][], int col) 
    { 
        
        Arrays.sort(arr, new Comparator<long[]>() { 
            
          @Override              
          
          public int compare(final long[] entry1,  
                             final long[] entry2) { 
  
            
            if (entry1[col] > entry2[col]) 
                return 1; 
            else
                return -1; 
          } 
        });  
    } 
    
    // Max contigious subArray sum
    static long func(long a[],int size,int s){
        long max1=a[s];
        long maxc=a[s];
        for(int i=s+1;i<size;i++){
            maxc=Math.max(a[i],maxc+a[i]);
            max1=Math.max(maxc,max1);
        }
        return max1;
    }
    public static class Pair<U extends Comparable<U>, V extends Comparable<V>> implements Comparable<Pair<U, V>> {
        public U x;
        public V y;
    
        public Pair(U x, V y) {
            this.x = x;
            this.y = y;
        }
    
        public int hashCode() {
            return (x == null ? 0 : x.hashCode() * 31) + (y == null ? 0 : y.hashCode());
        }
    
        public boolean equals(Object o) {
            if (this == o)
                return true;
            if (o == null || getClass() != o.getClass())
                return false;
            Pair<U, V> p = (Pair<U, V>) o;
            return (x == null ? p.x == null : x.equals(p.x)) && (y == null ? p.y == null : y.equals(p.y));
        }
    
        public int compareTo(Pair<U, V> b) {
            int cmpU = x.compareTo(b.x);
            return cmpU != 0 ? cmpU : y.compareTo(b.y);
        }
    
        public String toString() {
            return String.format("(%s, %s)", x.toString(), y.toString());
        }
    
    }

    // Combination 
    static long C(long n,long r){
        long count=0,temp=n;
        long ans=1;
        long num=n-r+1,div=1;
        while(num<=n){
            ans*=num;
            //ans+=MOD;
            ans%=MOD;
            ans*=mypow(div,MOD-2);
            //ans+=MOD;
            ans%=MOD;
            num++;
            div++;
        }
        
        ans+=MOD;
        return ans%MOD;
    }
    
    // Factorial
    static long fact(long a){
        long i,ans=1;
        for(i=1;i<=a;i++){
            ans*=i;
            ans%=MOD;
        }
        return ans%=MOD;
    }
    static void sieve(int n){
    	// Create a boolean array
        // "prime[0..n]" and
        // initialize all entries
        // it as true. A value in
        // prime[i] will finally be
        // false if i is Not a
        // prime, else true.
        boolean prime[] = new boolean[n + 1];
        for (int i = 0; i <= n; i++)
            prime[i] = true;
 
        for (int p = 2; p * p <= n; p++)
        {
            // If prime[p] is not changed, then it is a
            // prime
            if (prime[p] == true)
            {
                // Update all multiples of p
                for (int i = p * p; i <= n; i += p)
                    prime[i] = false;
            }
        }
 
        // Print all prime numbers
        for (int i = 2; i <= n; i++)
        {
            if (prime[i] == true)
            {
            	li.add(i);
            	
            }
        }
       
    }
    
    static void primeFactorSieve(int n){
        is_sieve[0]=1;
        is_sieve[1]=1;
        int i,j,k;
        for(i=2;i<n;i++){
            if(is_sieve[i]==0){
                sieve[i]=i;
                li.add(i);
                for(j=i*i;j<n;j+=i){
                    if(j>n||j<0){
                        break;
                    }
                    is_sieve[j]=1;
                    sieve[j]=i;
                }
            }
        }
    }
    
    static long mypow(long x,long y){
        long temp; 
        if( y == 0) 
            return 1; 
        temp = mypow(x, y/2); 
        if (y%2 == 0) 
            return (temp*temp)%MOD; 
        else
            return ((x*temp)%MOD*(temp)%MOD)%MOD; 
    }
    static long dist[],dp[][];
    static int visited[],isit[];
    static ArrayList<Integer> adj[],li;
    //static int dp[][][];
    static int MOD=1000000007,max=0;
    static char ch[];
    static int[] sieve,is_sieve;
    static TreeSet<Integer> tr;
    
    static int calcdist(int r1,int c1,int r2,int c2){
        if(r2-r1==c2-c1){
            return isRight(r1,c1)?0:r2-r1;
        }
        
        r2-=r1-1;
        c2-=c1-1;
        if(isLeft(r1,c1)){
            return (r2-c2)/2;
        }else{
            return (r2-c2+1)/2;
        }
    }
    
    static boolean isLeft(int r,int c){
        if((r+c)%2==0){
            return true;
        }
        return false;
    }
    
    static boolean isRight(int r,int c){
        if((r+c)%2!=0){
            return true;
        }
        return false;
    }
    static int binarySearch(List<Long> ll , long x) 
	{ 
		int l = 0, r = ll.size() - 1; 
		while (l <= r) { 
			int m = l + (r - l) / 2; 

			// Check if x is present at mid 
			if (ll.get(m) == x) 
				return m; 

			// If x greater, ignore left half 
			if (ll.get(m) < x) 
				l = m + 1; 

			// If x is smaller, ignore right half 
			else
				r = m - 1; 
		} 

		// if we reach here, then element was 
		// not present 
		return l-1; 
	} 
    
    public static char toCh(char c)
    {
    	int ch = Integer.parseInt(Character.toString(c));
    	
    	ch = (ch%9)+1;
    	
    	return Integer.toString(ch).charAt(0);
    }
    public static void main(String args[]){
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader sc = new InputReader(inputStream);
        PrintWriter w = new PrintWriter(outputStream);
        
        int n = sc.nextInt();
        
        String st = sc.next();
        char s[] = new char[n];
        s = st.toCharArray();
        li = new ArrayList<>();
        for(int i = 0;i<n-1;i++)
        {
        	if(s[i] == 'B')
        	{
        		if(s[i+1] == 'B')
        		{
        			li.add(i+1);
        			s[i] = 'W';
        			s[i+1] = 'W';
        			i++;
        		}
        		else
        		{
        			li.add(i+1);
        			s[i] = 'W';
        			s[i+1] = 'B';
        		}
        	}
        	
        	
        }
        if(s[n-1] == 'B')
    	{
    		if(n%2 == 0)
    			w.println(-1);
    		else
    		{
    			for(int i = 0;i<n-1;i+=2)
    				li.add(i+1);
    			
    			w.println(li.size());
        		for(int i : li)
        		{
        			w.print(i+" ");
        		}
    		}
    	}
    	else
    	{
    		w.println(li.size());
    		for(int i : li)
    		{
    			w.print(i+" ");
    		}
    	}
        
        w.close();
    }
}