There are 2N squares arranged from left to right. You are given a string of length 2N representing the color of each of the squares.

The color of the i-th square from the left is black if the i-th character of S is `B`, and white if that character is `W`.

You will perform the following operation exactly N times: choose two distinct squares, then invert the colors of these squares and the squares between them. Here, to invert the color of a square is to make it white if it is black, and vice versa.

Throughout this process, you cannot choose the same square twice or more. That is, each square has to be chosen exactly once.

Find the number of ways to make all the squares white at the end of the process, modulo 10^9+7.

Two ways to make the squares white are considered different if and only if there exists i (1 \leq i \leq N) such that the pair of the squares chosen in the i-th operation is different.

Constraints

* 1 \leq N \leq 10^5
* |S| = 2N
* Each character of S is `B` or `W`.

Input

Input is given from Standard Input in the following format:


N
S


Output

Print the number of ways to make all the squares white at the end of the process, modulo 10^9+7. If there are no such ways, print 0.

Examples

Input

2
BWWB


Output

4


Input

4
BWBBWWWB


Output

288


Input

5
WWWWWWWWWW


Output

0
import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.io.FilterInputStream;
import java.io.BufferedInputStream;
import java.io.InputStream;

/**
 * @author khokharnikunj8
 */

public class Main {
    public static void main(String[] args) {
        new Thread(null, new Runnable() {
            public void run() {
                new Main().solve();
            }
        }, "1", 1 << 26).start();
    }

    void solve() {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        ScanReader in = new ScanReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        CCellInversion solver = new CCellInversion();
        solver.solve(1, in, out);
        out.close();
    }

    static class CCellInversion {
        public void solve(int testNumber, ScanReader in, PrintWriter out) {
            int n = in.scanInt();
            char[] ar = in.scanChars(2 * n);
            long ans = 1;
            long mod = 1000000007;
            long Left = 1;
            long Right = 0;
            boolean[] checker = new boolean[2 * n];
            for (int i = 1; i < 2 * n; i++) {
                if (ar[i] != ar[i - 1]) {
                    checker[i] = checker[i - 1];
                } else {
                    checker[i] = checker[i - 1] ^ true;
                }
                if (checker[i]) {
                    ans = (ans * Math.max(Left - Right, 0)) % mod;
                    Right++;
                } else Left++;
            }
            if (Left != Right) ans = 0;
            if (ar[0] == 'W') ans = 0;
            if (ar[2 * n - 1] == 'W') ans = 0;
            for (int i = 1; i <= n; i++) {
                ans = (ans * i) % mod;
            }
            out.println(ans);
        }

    }

    static class ScanReader {
        private byte[] buf = new byte[4 * 1024];
        private int index;
        private BufferedInputStream in;
        private int total;

        public ScanReader(InputStream inputStream) {
            in = new BufferedInputStream(inputStream);
        }

        private int scan() {
            if (index >= total) {
                index = 0;
                try {
                    total = in.read(buf);
                } catch (Exception e) {
                    e.printStackTrace();
                }
                if (total <= 0) return -1;
            }
            return buf[index++];
        }

        public int scanInt() {
            int integer = 0;
            int n = scan();
            while (isWhiteSpace(n)) n = scan();
            int neg = 1;
            if (n == '-') {
                neg = -1;
                n = scan();
            }
            while (!isWhiteSpace(n)) {
                if (n >= '0' && n <= '9') {
                    integer *= 10;
                    integer += n - '0';
                    n = scan();
                }
            }
            return neg * integer;
        }

        public char[] scanChars(int n) {
            char[] ar = new char[n];
            int c = scan();
            boolean flag = true;
            while (isWhiteSpace(c)) c = scan();
            ar[0] = (char) c;
            for (int i = 1; i < n; i++) ar[i] = (char) (c = scan());
            return ar;
        }

        private boolean isWhiteSpace(int n) {
            if (n == ' ' || n == '\n' || n == '\r' || n == '\t' || n == -1) return true;
            else return false;
        }

    }
}

