#include <bits/stdc++.h>
using namespace std;
template <class T>
void read(T &x) {
  char c;
  bool op = 0;
  while (c = getchar(), c < '0' || c > '9')
    if (c == '-') op = 1;
  x = c - '0';
  while (c = getchar(), c >= '0' && c <= '9') x = x * 10 + c - '0';
  if (op) x = -x;
}
template <class T>
void write(T x) {
  if (x < 0) putchar('-'), x = -x;
  if (x >= 10) write(x / 10);
  putchar('0' + x % 10);
}
const int maxn = 2e5 + 5;
char s[maxn];
int color[maxn * 3];
struct Segment {
  int l, r, color;
} segment[maxn * 3];
int n, k, tot;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cin >> n >> k;
  cin >> (s + 1);
  for (int i = 1; i <= n; i++) color[i] = s[i] == 'B' ? 1 : 0;
  for (int i = n + 1; i <= 3 * n; i++) color[i] = color[(i - 1) % n + 1];
  for (int i = 1, j = 1; i <= 3 * n; i = j + 1) {
    while (j + 1 <= 3 * n && color[i] == color[j + 1]) ++j;
    if (j - i >= 1) segment[++tot] = {i, j, color[i]};
  }
  for (int i = 1; i < tot; i++) {
    int l = segment[i].r + 1, r = segment[i + 1].l - 1;
    int lc = color[l - 1], rc = color[r + 1];
    if (l > r) continue;
    int len = r - l + 1;
    if (2 * k >= len) {
      if (lc == rc) {
        for (int j = l; j <= r; j++) color[j] = lc;
      } else {
        for (int j = l; j <= l + len / 2 - 1; j++) color[j] = lc;
        for (int j = r; j >= r - len / 2 + 1; j--) color[j] = rc;
      }
    } else {
      for (int j = l; j <= l + k - 1; j++) color[j] = lc;
      for (int j = r; j >= r - k + 1; j--) color[j] = rc;
      for (int j = l + k; j <= r - k; j++) color[j] = !color[j - 1];
    }
  }
  if (tot == 0 && k % 2)
    for (int i = n + 1; i <= 2 * n; i++) color[i] = !color[i - 1];
  for (int i = n + 1; i <= 2 * n; i++) printf("%c", color[i] ? 'B' : 'W');
  return 0;
}
