#include <bits/stdc++.h>
using namespace std;
const int M = 4e5 + 5;
int n, k;
char c[M];
int is[M], d[M];
int main() {
  scanf("%d%d", &n, &k);
  scanf("%s", c + 1);
  bool flag = (n % 2 == 0);
  if (flag) {
    for (int i = 1; i < n; i++) {
      if (c[i] == c[i + 1]) {
        flag = false;
        break;
      }
    }
    if (flag) {
      for (int i = 1; i <= n; i++) {
        if (k & 1) {
          if (c[i] == 'W')
            putchar('B');
          else
            putchar('W');
        } else
          putchar(c[i]);
      }
      return 0;
    }
  }
  for (int i = 1; i <= n; i++) {
    int x = i - 1;
    if (x == 0) x = n;
    if (c[i] == c[x]) is[i] = 1;
    x = i + 1;
    if (x > n) x = 1;
    if (c[i] == c[x]) is[i] = 1;
  }
  for (int i = 1; i <= n; i++) {
    is[n + i] = is[i];
  }
  int last = -1;
  memset(d, 0x3f, sizeof d);
  for (int i = 1; i <= n + n; i++) {
    if (is[i] == 0 && last != -1) {
      d[i] = i - last;
    }
    if (is[i]) {
      last = i;
    }
  }
  last = -1;
  for (int i = n + n; i; i--) {
    if (is[i] == 0 && last != -1) {
      d[i] = min(d[i], last - i);
    }
    if (is[i]) {
      last = i;
    }
  }
  for (int i = 1; i <= n; i++) {
    if (is[i]) {
      putchar(c[i]);
      continue;
    }
    int x = min(k, min(d[i], d[i + n])) & 1;
    if (x) {
      if (c[i] == 'W')
        putchar('B');
      else
        putchar('W');
    } else {
      putchar(c[i]);
    }
  }
}
