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.util.*;
import java.io.*;
public class Main {
	public static void main(String[] args) {
		Solver solver = new Solver();
		solver.solve();
		solver.exit();
	}

	static class FastScanner {
		private final InputStream in = System.in;
		private final byte[] buffer = new byte[1024];
		private int ptr = 0;
		private int buflen = 0;
		private boolean hasNextByte() {
			if (ptr < buflen) {
				return true;
			}else{
				ptr = 0;
				try {
					buflen = in.read(buffer);
				} catch (IOException e) {
					e.printStackTrace();
				}
				if (buflen <= 0) {
					return false;
				}
			}
			return true;
		}
		private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
		private boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
		private void skipUnprintable() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;}
		public boolean hasNext() { skipUnprintable(); return hasNextByte();}
		public String next() {
			if (!hasNext()) throw new NoSuchElementException();
			StringBuilder sb = new StringBuilder();
			int b = readByte();
			while(isPrintableChar(b)) {
				sb.appendCodePoint(b);
				b = readByte();
			}
			return sb.toString();
		}
		public long nextLong() {
			if (!hasNext()) throw new NoSuchElementException();
			long n = 0;
			boolean minus = false;
			int b = readByte();
			if (b == '-') {
				minus = true;
				b = readByte();
			}
			if (b < '0' || '9' < b) {
				throw new NumberFormatException();
			}
			while(true){
				if ('0' <= b && b <= '9') {
					n *= 10;
					n += b - '0';
				}else if(b == -1 || !isPrintableChar(b)){
					return minus ? -n : n;
				}else{
					throw new NumberFormatException();
				}
				b = readByte();
			}
		}
	}

	static class Solver {
		FastScanner sc = new FastScanner();
		public Solver() { }

		String ns() { return sc.next(); }
		String[] ns(int n) {
			String a[] = new String[n];
			for(int i = 0; i < n; i ++) { a[i] = ns(); }
			return a;
		}
		String[][] ns(int n, int m) {
			String a[][] = new String[n][m];
			for(int i = 0; i < n; i ++) { a[i] = ns(m); }
			return a;
		}
		char[] nc() {
			String str = ns();
			char a[] = new char[str.length()];
			for(int i = 0; i < str.length(); i ++) { a[i] = str.charAt(i); }
			return a;
		}
		char[][] nc(int n, int m) {
			char a[][] = new char[n][m];
			for(int i = 0; i < n; i ++) { a[i] = nc(); }
			return a;
		}
		boolean[] nb(int n, char t) {
			boolean a[] = new boolean[n];
			char c[] = nc();
			for(int i = 0; i < n; i ++) { a[i] = c[i] == t; }
			return a;
		}
		boolean[][] nb(int n, int m, char t) {
			boolean a[][] = new boolean[n][m];
			for(int i = 0; i < n; i ++) { a[i] = nb(m, t); }
			return a;
		}
		int ni() { return (int)sc.nextLong(); }
		int[] ni(int n) {
			int a[] = new int[n];
			for(int i = 0; i < n; i ++) { a[i] = ni(); }
			return a;
		}
		int[][] ni(int n, int m) {
			int a[][] = new int[n][m];
			for(int i = 0; i < n; i ++) { a[i] = ni(m); }
			return a;
		}
		long nl() { return sc.nextLong(); }
		long[] nl(int n) {
			long a[] = new long[n];
			for(int i = 0; i < n; i ++) { a[i] = nl(); }
			return a;
		}
		long[][] nl(int n, int m) {
			long a[][] = new long[n][m];
			for(int i = 0; i < n; i ++) { a[i] = nl(m); }
			return a;
		}

		PrintWriter out = new PrintWriter(System.out);
		PrintWriter err = new PrintWriter(System.err);
		void prt() { out.print(""); }
		void prt(int a) { out.print(a); }
		void prt(long a) { out.print(a); }
		void prt(double a) { out.print(a); }
		void prt(String a) { out.print(a); }
		void prtln() { out.println(""); }
		void prtln(int a) { out.println(a); }
		void prtln(long a) { out.println(a); }
		void prtln(double a) { out.println(a); }
		void prtln(String a) { out.println(a); }
		void prtln(int... a) {
			StringBuilder sb = new StringBuilder();
			for(int element : a){ sb.append(element+" "); }
			prtln(sb.toString().trim());
		}
		void prtln(long... a) {
			StringBuilder sb = new StringBuilder();
			for(long element : a){ sb.append(element+" "); }
			prtln(sb.toString().trim());
		}
		void prtln(double... a) {
			StringBuilder sb = new StringBuilder();
			for(double element : a){ sb.append(element+" "); }
			prtln(sb.toString().trim());
		}
		void prtln(String... a) {
			StringBuilder sb = new StringBuilder();
			for(String element : a){ sb.append(element+" "); }
			prtln(sb.toString().trim());
		}
		void prtln(int[][] a) { for(int[] element : a){ prtln(element); } }
		void prtln(long[][] a) { for(long[] element : a){ prtln(element); } }
		void prtln(double[][] a) { for(double[] element : a){ prtln(element); } }
		void prtln(String[][] a) { for(String[] element : a){ prtln(element); } }
		void errprt() { err.print(""); }
		void errprt(int a) { err.print(a); }
		void errprt(long a) { err.print(a); }
		void errprt(double a) { err.print(a); }
		void errprt(String a) { err.print(a); }
		void errprt(boolean a) { errprt(a ? "#" : "."); }
		void errprtln() { err.println(""); }
		void errprtln(int a) { err.println(a); }
		void errprtln(long a) { err.println(a); }
		void errprtln(double a) { err.println(a); }
		void errprtln(String a) { err.println(a); }
		void errprtln(boolean a) { errprtln(a ? "#" : "."); }
		void errprtln(int... a) {
			StringBuilder sb = new StringBuilder();
			for(int element : a){ sb.append(element+" "); }
			errprtln(sb.toString().trim());
		}
		void errprtln(long... a) {
			StringBuilder sb = new StringBuilder();
			for(long element : a){ sb.append(element+" "); }
			errprtln(sb.toString().trim());
		}
		void errprtln(double... a) {
			StringBuilder sb = new StringBuilder();
			for(double element : a){ sb.append(element+" "); }
			errprtln(sb.toString().trim());
		}
		void errprtln(String... a) {
			StringBuilder sb = new StringBuilder();
			for(String element : a){ sb.append(element+" "); }
			errprtln(sb.toString().trim());
		}
		void errprtln(boolean... a) {
			StringBuilder sb = new StringBuilder();
			for(boolean element : a){ sb.append(element+" "); }
			errprtln(sb.toString().trim());
		}
		void errprtln(int[][] a) { for(int[] element : a){ errprtln(element); } }
		void errprtln(long[][] a) { for(long[] element : a){ errprtln(element); } }
		void errprtln(double[][] a) { for(double[] element : a){ errprtln(element); } }
		void errprtln(String[][] a) { for(String[] element : a){ errprtln(element); } }
		void errprtln(boolean[][] a) { for(boolean[] element : a){ errprtln(element); } }
		void reply(boolean b) { prtln(b ? "Yes" : "No"); }
		void REPLY(boolean b) { prtln(b ? "YES" : "NO"); }

		void exit() { out.flush(); err.flush(); System.exit(0); }

		int min(int a, int b) { return Math.min(a, b); }
		long min(long a, long b) { return Math.min(a, b); }
		double min(double a, double b) { return Math.min(a, b); }
		int min(int... x) {
			int min = x[0];
			for(int val : x) { min = min(min, val); }
			return min;
		}
		long min(long... x) {
			long min = x[0];
			for(long val : x) { min = min(min, val); }
			return min;
		}
		double min(double... x) {
			double min = x[0];
			for(double val : x) { min = min(min, val); }
			return min;
		}
		int max(int a, int b) { return Math.max(a, b); }
		long max(long a, long b) { return Math.max(a, b); }
		double max(double a, double b) { return Math.max(a, b); }
		int max(int... x) {
			int max = x[0];
			for(int val : x) { max = max(max, val); }
			return max;
		}
		long max(long... x) {
			long max = x[0];
			for(long val : x) { max = max(max, val); }
			return max;
		}
		double max(double... x) {
			double max = x[0];
			for(double val : x) { max = max(max, val); }
			return max;
		}
		long sum(int... a) {
			long sum = 0;
			for(int element : a) { sum += element; }
			return sum;
		}
		long sum(long... a) {
			long sum = 0;
			for(long element : a) { sum += element; }
			return sum;
		}
		double sum(double... a) {
			double sum = 0;
			for(double element : a) { sum += element; }
			return sum;
		}

		long abs(double x) { return (long)Math.abs(x); }
		long round(double x) { return Math.round(x); }
		long floor(double x) { return (long)Math.floor(x); }
		long ceil(double x) { return (long)Math.ceil(x); }
		double sqrt(double x) { return Math.sqrt(x); }
		double pow(double x, double y) { return Math.pow(x, y); }
		long pow(long x, long y) { return (long)Math.pow(x, y); }
		int gcd(int a, int b) { return b == 0 ? a : gcd(b, a % b); }
		long gcd(long a, long b) { return b == 0 ? a : gcd(b, a % b); }

		long[] div(long a) {
			List<Long> divList = new ArrayList<Long>();
			for(long i = 1; i * i <= a; i ++) {
				if(a % i == 0) {
					divList.add(i);
					if(i * i != a) { divList.add(a / i); };
				}
			}

			long div[] = new long[divList.size()];
			for(int i = 0; i < divList.size(); i ++) { div[i] = divList.get(i); }
			return div;
		}

		int numDigits(long a) { return Long.toString(a).length(); }
		long bitFlag(int a) { return 1L << (long)a; }
		boolean isFlagged(long x, int a) { return (x & bitFlag(a)) != 0; }
 
		long countString(String str, String a) { return str.length() - str.replace(a, "").length(); }

		void reverse(String array[]) {
			String reversed[] = new String[array.length];
			for(int i = 0; i < array.length; i ++) { reversed[array.length - i - 1] = array[i]; }
			for(int i = 0; i < array.length; i ++) { array[i] = reversed[i]; }
		}
		void reverse(int array[]) {
			int reversed[] = new int[array.length];
			for(int i = 0; i < array.length; i ++) { reversed[array.length - i - 1] = array[i]; }
			for(int i = 0; i < array.length; i ++) { array[i] = reversed[i]; }
		}
		void reverse(long array[]) {
			long reversed[] = new long[array.length];
			for(int i = 0; i < array.length; i ++) { reversed[array.length - i - 1] = array[i]; }
			for(int i = 0; i < array.length; i ++) { array[i] = reversed[i]; }
		}
		void reverse(double array[]) {
			double reversed[] = new double[array.length];
			for(int i = 0; i < array.length; i ++) { reversed[array.length - i - 1] = array[i]; }
			for(int i = 0; i < array.length; i ++) { array[i] = reversed[i]; }
		}
		void reverse(boolean array[]) {
			boolean reversed[] = new boolean[array.length];
			for(int i = 0; i < array.length; i ++) { reversed[array.length - i - 1] = array[i]; }
			for(int i = 0; i < array.length; i ++) { array[i] = reversed[i]; }
		}
		void fill(int array[], int x) { Arrays.fill(array, x); }
		void fill(long array[], long x) { Arrays.fill(array, x); }
		void fill(double array[], double x) { Arrays.fill(array, x); }
		void fill(boolean array[], boolean x) { Arrays.fill(array, x); }
		void fill(int array[][], int x) { for(int a[] : array) { fill(a, x); } }
		void fill(long array[][], long x) { for(long a[] : array) { fill(a, x); } }
		void fill(double array[][], double x) { for(double a[] : array) { fill(a, x); } }
		void fill(boolean array[][], boolean x) { for(boolean a[] : array) { fill(a, x); } }

		long INF = (long)1e+15;
		boolean isINF(long a) { return abs(a) > INF / 1000; }
		boolean isPlusINF(long a) { return a > 0 && isINF(a); }
		boolean isMinusINF(long a) { return isPlusINF(- a); }


		// mods
		long MOD = (long)1e+9 + 7; // 998244353
		public long mod(long i) { return i % MOD + ((i % MOD) < 0 ? MOD : 0); }
		
		long pow_m(long x, long y) {
			if (y == 0) { return 1;
			}else {
				long tmp = pow_m(x, y / 2);
				return mod(mod(tmp * tmp) * (y % 2 == 0 ? 1 : x));
			}
		}
		
		long inv(long x) { return pow_m(x, MOD - 2); }
		
		int MAX_FACT = 5_000_100;
		long fact[];
		long invFact[];
		void prepareFact() {
			fact = new long[MAX_FACT];
			Arrays.fill(fact, 0);
			invFact = new long[MAX_FACT];
			Arrays.fill(invFact, 0);
			fact[0] = 1;
			int maxIndex = min(MAX_FACT, (int)MOD);
			for(int i = 1; i < maxIndex; i ++) { fact[i] = mod(fact[i - 1] * i); }
			invFact[maxIndex - 1] = inv(fact[maxIndex - 1]);
			for(int i = maxIndex - 1; i > 0; i --) { invFact[i - 1] = mod(invFact[i] * i); }
		}
		
		long P(int n, int r) {
			if(n < 0 || r < 0 || n < r) { return 0; }
			return mod(fact[n] * invFact[n - r]);
		}
		long C(int n, int r) {
			if(n < 0 || r < 0 || n < r) { return 0; }
			return mod(P(n, r) * invFact[r]);
		}
		long H(int n, int r) { return C((n - 1) + r, r); }

		// grid
		class Grid {
			int h;
			int w;

			Grid() {  }
			Grid(int h, int w) {
				this.h = h;
				this.w = w;
			}
		}


		// graph
		class Graph {
			int numNode;
			int numEdge;
			Edge edges[];
			Node nodes[];
			Node reversedNodes[];

			Graph(int numNode, int numEdge, Edge edges[], boolean directed) {
				this.numNode = numNode;
				this.numEdge = numEdge;
				this.edges = edges;
				nodes = new Node[numNode];
				reversedNodes = new Node[numNode];
				for(int i = 0; i < numNode; i ++) {
					nodes[i] = new Node(i);
					reversedNodes[i] = new Node(i);
				}

				for(Edge edge : edges) {
					nodes[edge.source].add(edge.target, edge.cost);
					if(directed) {
						reversedNodes[edge.target].add(edge.source, edge.cost);
					}else {
						nodes[edge.target].add(edge.source, edge.cost);
					}
				}
			}

			void clearNodes() {
				for(Node n : nodes) { n.clear(); }
				for(Node n : reversedNodes) { n.clear(); }
			}
		}

		class Node {
			int id;
			ArrayList<Edge> edges = new ArrayList<Edge>();

			Node(int id) {
				this.id = id;
			}
			void add(int target, long cost) {
				edges.add(new Edge(id, target, cost));
			}
			void clear() {
				edges.clear();
			}
		}

		class Edge implements Comparable<Edge> {
			int source;
			int target;
			long cost;
			Edge(int source, int target, long cost) {
				this.source = source;
				this.target = target;
				this.cost = cost;
			}

			@Override
			public int compareTo(Edge e) {
				return Long.compare(this.cost, e.cost);
			}
		}

public void solve() {
	prepareFact();
	int num = ni();
	num *= 2;
	boolean isBlack[] = nb(num, 'B');
	int a[] = new int[num];
	long sum = 0;
	for(int i = 0; i < num; i ++) {
		a[i] = ((isBlack[i] ? 1 : 0) + sum) % 2 != 0 ? 1 : -1;
		sum += a[i];
		sum %= 2;
	}
	sum = 0;
	for(int i = 0; i < num; i ++) {
		sum += a[i];
		if(sum < 0) {
			prtln(0); return;
		}
	}
	if(sum != 0) {
		prtln(0); return;
	}
	long ans = 1;
	long count = 0;
	for(int i = 0; i < num; i ++) {
		if(a[i] > 0) { count ++; }
		else { ans = mod(ans * count); count --; }
	}
	ans = mod(ans * fact[num / 2]);
	prtln(ans);
}


	}
}