package main

import (
	"bufio"
	"io"
	"os"
)

var data []byte
var idx int

func nextInt() int {
	for idx < len(data) && data[idx] <= ' ' {
		idx++
	}
	sign := 1
	if idx < len(data) && data[idx] == '-' {
		sign = -1
		idx++
	}
	val := 0
	for idx < len(data) && data[idx] > ' ' {
		val = val*10 + int(data[idx]-'0')
		idx++
	}
	return sign * val
}

func nextString() string {
	for idx < len(data) && data[idx] <= ' ' {
		idx++
	}
	start := idx
	for idx < len(data) && data[idx] > ' ' {
		idx++
	}
	return string(data[start:idx])
}

func flip(c byte) byte {
	if c == 'W' {
		return 'B'
	}
	return 'W'
}

func main() {
	data, _ = io.ReadAll(os.Stdin)

	n := nextInt()
	k := nextInt()
	s := []byte(nextString())

	good := make([]bool, n)
	has := false
	for i := 0; i < n; i++ {
		j := i + 1
		if j == n {
			j = 0
		}
		if s[i] == s[j] {
			good[i] = true
			good[j] = true
			has = true
		}
	}

	res := make([]byte, n)

	if !has {
		if k%2 == 0 {
			copy(res, s)
		} else {
			for i := 0; i < n; i++ {
				res[i] = flip(s[i])
			}
		}
		w := bufio.NewWriterSize(os.Stdout, 1<<20)
		w.Write(res)
		w.Flush()
		return
	}

	dist := make([]int, n)
	for i := 0; i < n; i++ {
		dist[i] = -1
	}
	color := make([]byte, n)
	q := make([]int, 0, n)

	for i := 0; i < n; i++ {
		if good[i] {
			dist[i] = 0
			color[i] = s[i]
			q = append(q, i)
		}
	}

	for head := 0; head < len(q); head++ {
		v := q[head]

		u := v - 1
		if u < 0 {
			u = n - 1
		}
		if dist[u] == -1 {
			dist[u] = dist[v] + 1
			color[u] = color[v]
			q = append(q, u)
		}

		u = v + 1
		if u == n {
			u = 0
		}
		if dist[u] == -1 {
			dist[u] = dist[v] + 1
			color[u] = color[v]
			q = append(q, u)
		}
	}

	parity := k % 2
	for i := 0; i < n; i++ {
		if dist[i] <= k {
			res[i] = color[i]
		} else {
			if parity == 0 {
				res[i] = s[i]
			} else {
				res[i] = flip(s[i])
			}
		}
	}

	w := bufio.NewWriterSize(os.Stdout, 1<<20)
	w.Write(res)
	w.Flush()
}