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 javax.print.DocFlavor;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.nio.charset.IllegalCharsetNameException;
import java.sql.SQLOutput;
import java.util.*;



public class Main {
    static int[] arr;
    static boolean[] v;
    static long[] ans;
    static int n;
    static int[] parity;

    public static void main(String[] args) throws IOException{
        Reader.init(System.in);
        int n = Reader.nextInt();
        String s = Reader.next();
        int[] arr = new int[n];
        int cnt1 = 0;
        int cnt2 = 0;
        Deque<Integer> q = new LinkedList<>();
        Deque<Integer> qq = new LinkedList<>();
        for (int i = 0 ; i < n ; i++){
            if (s.charAt(i)=='B'){
                arr[i] = 1;
                cnt1++;
                q.addLast(i);
            }
            else{
                qq.addLast(i);
            }

        }
        int r = 0;
        Deque<Integer> ans = new LinkedList<>();
        cnt2 = n - cnt1;
        if (cnt1%2==0 || cnt2%2==0){
            if (cnt1%2==0){
                while (q.isEmpty()==false){
                    int first = q.removeFirst();
                    int second = q.removeFirst();
                    for (int i = second -1 ; i >= first ; i--){
                        r++;
                        ans.addLast(i);
                    }
                }

            }
            else{
                while (qq.isEmpty()==false){
                    int first = qq.removeFirst();
                    int second = qq.removeFirst();
                    for (int i = second -1 ; i >= first ; i--){
                        r++;
                        ans.addLast(i);
                    }
                }
            }
            System.out.println(r);
            while (ans.isEmpty()==false){
                System.out.print((ans.removeFirst()+1) + " ");
            }
        }
        else{
            System.out.println(-1);
        }


    }

    static long fun(int pp , int i  , int hops){
        if (i<0 || i >= n){
            return Long.MAX_VALUE;
        }
        if (v[i]==true){
            if ((pp ^ parity[i])==1){
                return hops;
            }
            else{
                if (ans[i]==Long.MAX_VALUE) {
                    return Long.MAX_VALUE;
                }
                else{
                    return ans[i] + 1;
                }
            }
        }
        if ((pp ^ parity[i])==1){
            return 1;
        }
        v[i] = true;
        long num1 = fun(parity[i] , i + arr[i] , 1);
        long num2 = fun(parity[i] , i - arr[i] , 1);
        ans[i] = Math.min(num1,num2);
        if (ans[i]==Long.MAX_VALUE){
            return ans[i];
        }
        else{
            return ans[i] + 1;
        }

    }







    /*static int find(int x) {
        return parent[x] == x ? x : (parent[x] = find(parent[x]));
    }
    static void merge(int x, int y) {
        x = find(x);
        y = find(y);
        if ( x > y ){
            parent[y] = x;
        }
        else if (y > x){
            parent[x] = y;
        }
    }*/

    static Deque<Integer>[] graph ;

    static void solve()throws IOException{
        int n = Reader.nextInt();






    }

    static int dfs(int start , int cannot){
        if (start==cannot){
            return 0;
        }
        v[start] = true;
        Iterator i = graph[start].iterator();
        int cnt = 1;
        while (i.hasNext()){
            int next = (int)i.next();
            if (!v[next]){
                cnt+=dfs(next,cannot);
            }
        }
        return cnt;
    }


    public static void sortbyColumn(int arr[][], int col)
    {
        // Using built-in sort function Arrays.sort
        Arrays.sort(arr, new Comparator<int[]>() {

            @Override
            // Compare values according to columns
            public int compare(final int[] entry1,
                               final int[] entry2) {

                // To sort in descending order revert
                // the '>' Operator
                if (entry1[col] > entry2[col])
                    return 1;
                else
                    return -1;
            }
        });  // End of function call sort().
    }


    static class Node{
        long a;
        int i;
        Node(long a, int i){
            this.a = a;
            this.i = i;
        }
    }

}


class Reader {
    static BufferedReader reader;
    static StringTokenizer tokenizer;

    /** call this method to initialize reader for InputStream */
    static void init(InputStream input) {
        reader = new BufferedReader(
                new InputStreamReader(input) );
        tokenizer = new StringTokenizer("");
    }
    /** get next word */
    static String next() throws IOException {
        while ( ! tokenizer.hasMoreTokens() ) {
            //TODO add check for eof if necessary
            tokenizer = new StringTokenizer(
                    reader.readLine() );
        }
        return tokenizer.nextToken();
    }

    static int nextInt() throws IOException {
        return Integer.parseInt( next() );
    }
    static long nextLong() throws IOException {
        return Long.parseLong( next() );
    }

    static double nextDouble() throws IOException {
        return Double.parseDouble( next() );
    }
}
class MergeSort
{
    // Merges two subarrays of arr[].
    // First subarray is arr[l..m]
    // Second subarray is arr[m+1..r]
    void merge(int arr[], int l, int m, int r)
    {
        // Find sizes of two subarrays to be merged
        int n1 = m - l + 1;
        int n2 = r - m;

        /* Create temp arrays */
        int L[] = new int [n1];
        int R[] = new int [n2];

        /*Copy data to temp arrays*/
        for (int i=0; i<n1; ++i)
            L[i] = arr[l + i];
        for (int j=0; j<n2; ++j)
            R[j] = arr[m + 1+ j];


        /* Merge the temp arrays */

        // Initial indexes of first and second subarrays
        int i = 0, j = 0;

        // Initial index of merged subarry array
        int k = l;
        while (i < n1 && j < n2)
        {
            if (L[i] <= R[j])
            {
                arr[k] = L[i];
                i++;
            }
            else
            {
                arr[k] = R[j];
                j++;
            }
            k++;
        }

        /* Copy remaining elements of L[] if any */
        while (i < n1)
        {
            arr[k] = L[i];
            i++;
            k++;
        }

        /* Copy remaining elements of R[] if any */
        while (j < n2)
        {
            arr[k] = R[j];
            j++;
            k++;
        }
    }

    // Main function that sorts arr[l..r] using
    // merge()
    void sort(int arr[], int l, int r)
    {
        if (l < r)
        {
            // Find the middle point
            int m = (l+r)/2;

            // Sort first and second halves
            sort(arr, l, m);
            sort(arr , m+1, r);

            // Merge the sorted halves
            merge(arr, l, m, r);
        }
    }

    /* A utility function to print array of size n */
    static void printArray(int arr[])
    {
        int n = arr.length;
        for (int i=0; i<n; ++i)
            System.out.print(arr[i] + " ");
        System.out.println();
    }

    // Driver method

}

class Node implements Comparable<Node>{
    int a;
    int b;
    Node (int a , int b){
        this.a = a;
        this.b = b;
    }



    public int compareTo(Node o) {
        if ((this.a%2) == (o.a%2)){
            return (this.b - o.b);
        }
        else{
            return this.a - o.a;
        }
    }
}