fun main(args: Array<String>) = IO().exec {
    val n = int()
    val s = string().toCharArray()
    println(calc(n, s) * fact(co(n.toLong())))
}

fun fact(n: Co):Co = if (n == co(1)) co(1) else n * fact(n - co(1))

fun calc(n: Int, s: CharArray): Co {
    for (i in 0 until 2*n step 2) s[i] = rev(s[i])
    if (s.count{it == 'B'} != n) return co(0)
    var cnt = 0L
    var ret = co(1)
    for (i in 2*n) {
        if (s[i] == 'W') cnt++
        else {
            if (cnt == 0L) return co(0)
            ret *= co(cnt)
            cnt--
        }
    }
    return ret
}

fun rev(c: Char) = if (c == 'B') 'W' else 'B'

const val M = 1000000007L

fun co(n: Long) = Co(n % M)

data class Co(val n: Long) {
    override fun toString(): String = n.toString()
    operator fun plus(other: Co): Co {
        return co(n + other.n)
    }
    operator fun minus(other: Co): Co {
        return co((n - other.n) % M + M)
    }
    operator fun times(other: Co): Co {
        return co(n * other.n)
    }
    operator fun div(other: Co): Co {
        return this * other.pow(M - 2)
    }
    fun pow(k_: Long): Co {
        var k = k_
        var a = this
        var res = co(1)
        while (k > 0) {
            if (k.and(1) == 1L) {
                res *= a
            }
            a *= a
            k = k.shr(1)
        }
        return res
    }
}

// region template
operator fun Int.iterator() = 0.until(this).iterator()

class IO {
    val printable = 33..126
    val buffer = ByteArray(1024)
    var ptr = 0
    var buflen = 0
    val out = java.io.PrintWriter(System.out)
    fun hasNextByte(): Boolean = if (ptr < buflen) true else {
        ptr = 0
        buflen = System.`in`.read(buffer)
        buflen > 0
    }

    fun readByte(): Byte = if (hasNextByte()) buffer[ptr++] else -1
    fun hasNext(): Boolean {
        while (hasNextByte() && buffer[ptr] !in printable) ptr++
        return hasNextByte()
    }

    fun string(): String {
        if (!hasNext()) throw java.util.NoSuchElementException()
        val sb = StringBuilder()
        var b = readByte()
        while (b in printable) {
            sb.appendCodePoint(b.toInt())
            b = readByte()
        }
        return sb.toString()
    }

    fun long(): Long {
        if (!hasNext()) throw java.util.NoSuchElementException()
        var n = 0L
        var minus = false
        var b = readByte()
        if (b == '-'.toByte()) {
            minus = true
            b = readByte()
        }
        if (b !in '0'.toByte()..'9'.toByte()) {
            throw NumberFormatException()
        }
        while (true) {
            if (b in '0'.toByte()..'9'.toByte()) {
                n *= 10
                n += b - '0'.toByte()
            } else if (b == (-1).toByte() || b !in printable) {
                return if (minus) -n else n
            } else {
                throw NumberFormatException()
            }
            b = readByte()
        }
    }

    fun int(): Int {
        val nl = long()
        if (nl !in Integer.MIN_VALUE..Integer.MAX_VALUE) throw NumberFormatException()
        return nl.toInt()
    }

    fun double(): Double = string().toDouble()
    fun print(obj: Any) = out.print(obj)
    fun print(i: Int) = out.print(i)
    fun print(l: Long) = out.print(l)
    fun println(obj: Any) = out.println(obj)
    fun println(i: Int) = out.println(i)
    fun println(l: Long) = out.println(l)
    inline fun exec(block: IO.() -> Unit) {
        block()
        out.flush()
    }
}
// endregion

Measured memory_bytes: 44652