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 Main {
    public static PrintStream out = new PrintStream(System.out);;
    public static void main(String[] args){
      FastScanner sc = new FastScanner();
      int countW = 0; int countB = 0;
      int n = sc.nextInt();
      String s = sc.nextLine();
      char[] arr = s.toCharArray();
      int l = arr.length;
      //try white
      boolean whiteok = false;
      ArrayList<Integer> v = new ArrayList();
          boolean blackok = false;
          ArrayList<Integer> v2 = new ArrayList();
      for(int i = 0; i < l; i++){
          if(i == l - 1){
              if(arr[i] == 'W') whiteok = true;
          } else{
            if(arr[i] != 'W'){
               arr[i] = 'W';
               if(arr[i + 1] == 'B') arr[i + 1] = 'W';
               else arr[i + 1] = 'B';
               v.add(i + 1);
            }
          }
      }
      if(whiteok){
          out.println(v.size());
          for(int i : v)
              out.print(i + " ");
          out.println();
      }
      else{
          //try black
          arr = s.toCharArray();
          for(int i = 0; i  < l; i++){
              if(i == l - 1){
                  if(arr[i] == 'B') blackok = true;
              } else{
                  if(arr[i] != 'B'){
                      arr[i] = 'B';
                      if(arr[i + 1] == 'B') arr[i + 1] = 'W';
                      else arr[i + 1] = 'B';
                      v2.add(i + 1);
                  }
              }
          }
          if(blackok){
            out.println(v2.size());
            for(int i : v2)
                out.print(i + " ");
            out.println();
          }
          else out.println("-1");
      }
      
      
      
    }
    
    
    
    
    
    
    private static int factorial(int n){
            int fac = 1;
            for(int i=2;i<=n;i++){
                    fac *= i;
            }

            return fac;
    }
    
    private static boolean isPrime(int n){
            if(n == 0 || n == 1){
                    return false;
            }else if(n%2 == 0){
                    return false;
            }else{
                    int x = (int)(Math.sqrt(n)) + 1;
                    for(int i=3;i<=x;i+=2){
                            if(n % i == 0){
                                    return false;
                            }
                    }
                    return true;
            }
    }

    private static long pow(int base,int exp){
            if(exp == 0){
                    return 1;
            }else if(exp == 1){
                    return base;
            }else{
                    long a = pow(base,exp/2);
                    if(exp%2 == 0){
                            return a * a;
                    }else{
                            return a * a * base;
                    }
            }

    }

    private static int gcd(int a,int b){
            if(a == 0){
                    return b;
            }

            return gcd(b%a,a);
    }

    private static int lcm(int a,int b){
            return (a * b)/gcd(a,b);
    }
    private static ArrayList<Integer> SieveOfEratosthenes(int n){
        boolean b[] = new boolean[n+1];
        b[0] = true;
        b[1] = true;
        for(int i=2;i<=5;i++){
                int j = 2;
                while(i * j <= n && !b[i]){
                        b[i * j] = true;
                        j++;
                }
        }

        ArrayList<Integer> arr = new ArrayList<>();
        for(int i=2;i<n+1;i++){
                if(!b[i]){
                        arr.add(i);
                }
        }

        return arr;
    }
 
}




class FastScanner 
    { 
        BufferedReader br; 
        StringTokenizer st; 
  
        public FastScanner() 
        { 
            br = new BufferedReader(new
                     InputStreamReader(System.in)); 
        } 
  
        String next() 
        { 
            while (st == null || !st.hasMoreElements()) 
            { 
                try
                { 
                    st = new StringTokenizer(br.readLine()); 
                } 
                catch (IOException  e) 
                { 
                    e.printStackTrace(); 
                } 
            } 
            return st.nextToken(); 
        } 
  
        int nextInt() 
        { 
            return Integer.parseInt(next()); 
        } 
  
        long nextLong() 
        { 
            return Long.parseLong(next()); 
        } 
  
        double nextDouble() 
        { 
            return Double.parseDouble(next()); 
        } 
  
        String nextLine() 
        { 
            String str = ""; 
            try
            { 
                str = br.readLine(); 
            } 
            catch (IOException e) 
            { 
                e.printStackTrace(); 
            } 
            return str; 
        } 
    } 




//class Node
//{
//    public int V;
//    public Node(int v)
//    {
//        this.V=v;
//    }
//}


//class Node implements Comparable<Node>
//{
//    public int V,E;
//    public Node(int v, int e)
//    {
//        this.V=v;
//        this.E=e;
//    }
//    public int compareTo( Node N ){
//        return E - N.E;
//    }
//}




//    class Graph{
//        int V; 
//        LinkedList<Integer>[] adjListArray; 
//
//        Graph(int V) { 
//            this.V = V; 
//            // define the size of array as 
//            // number of vertices 
//            adjListArray = new LinkedList[V + 5]; 
//
//            // Create a new list for each vertex 
//            // such that adjacent nodes can be stored 
//
//            for(int i = 0; i < V + 5; i++){ 
//                adjListArray[i] = new LinkedList<Integer>(); 
//            } 
//        } 
//
//        void addEdge( int src, int dest) { 
//            adjListArray[src].add(dest); 
//            adjListArray[dest].add(src); 
//        } 
//
//           void DFSUtil(int v, boolean[] visited) { 
//            // Mark the current node as visited and print it 
//            visited[v] = true; 
//            q.add(v);
//            //System.out.print(v+" "); 
//            // Recur for all the vertices 
//            // adjacent to this vertex 
//            for (int x : adjListArray[v]) { 
//                if(!visited[x]) DFSUtil(x,visited); 
//            } 
//
//        } 
//
//        void connectedComponents(){
//            boolean[] visited = new boolean[V + 5]; 
//            boolean found = true;
//            for(int v = 1; v <= V; ++v) { 
//                if(!visited[v]) { 
//                    // print all reachable vertices 
//                    // from v 
//                    q = new LinkedList();
//                    DFSUtil(v,visited); 
//                    found = true;
//                    if(q.size() < 3){
//                        found = false;
//                        continue;
//                    }
//                    for(int i = 0; i < q.size(); i++){
//                        if(adjListArray[q.get(i)].size() != q.size() - 1){
//                            found = false;
//                            System.out.println("yo");
//                            System.out.println("i: " + i + " size: " + adjListArray[i].size());
//                            break;
//                        }
//                    }
//                    if(found){
//                        ok = true;
//                        break;
//                    }
//                    //System.out.println(); 
//                    //System.out.println("size: " + q.size());
//                } 
//            }
//            
//        }
//    }


//        N = sc.nextInt();
//        M = sc.nextInt();
//        adj=new LinkedList[N + 5];
//        for(int i = 0; i <= N + 4; i++)
//            adj[i] = new LinkedList();
//        
//        for(int i = 0; i < M; i++){
//            int u = sc.nextInt(); int v = sc.nextInt(); int e = sc.nextInt();
//            adj[u].add(new Node(v, e)); adj[v].add(new Node(u, e));
//        }
//        vis = new int[N + 5];
//        for(int i = 0; i < N + 5; i++)
//            vis[i] = Integer.MAX_VALUE;
//        vis[1] = 0;
//        pq.offer(new Node(1, 0));
//        ArrayList<Integer> path = new ArrayList();
//        path.add(1);
//        while(pq.size() > 0){
//            Node n = pq.poll();
//            Iterator<Node> i = adj[n.V].listIterator();
//            while(i.hasNext())
//            {
//                Node v=i.next();
//                if(n.E+v.E<vis[v.V])
//                {
//                    vis[v.V]=n.E+v.E;
//                    pq.offer(new Node(v.V,vis[v.V]));
//                    path.add(v.V);
//                }
//            }
//            
//        }
//        path.add(N);
//        for(int i = 0; i < path.size(); i++)
//            System.out.print(path.get(i) + " ");
//        System.out.println();