#include <bits/stdc++.h>
using namespace std;
const int maxn = 4e5 + 5;
char s[maxn];
int a[maxn], n, k;
char change(char a) { return 'B' + 'W' - a; }
int get_nxt(int i) { return (i + 1) % n; }
int get_pre(int i) { return (i + n - 1) % n; }
int predo(int n) {
  int ret = 0, flag = 0;
  for (int i = 0; i < n; ++i) {
    if (s[get_pre(i)] == s[i] || s[get_nxt(i)] == s[i]) {
      a[i] = 1;
      flag |= 1;
    } else {
      a[i] = 0;
      flag |= 2;
    }
  }
  if (flag == 1) return -1;
  if (flag == 2) return -2;
  for (int i = 0; i < n; ++i) {
    if (!a[get_pre(i)] && a[i]) {
      ret = i;
      break;
    }
  }
  return ret;
}
int main() {
  while (~scanf("%d%d", &n, &k)) {
    scanf("%s", s);
    int st = predo(n);
    if (st < 0) {
      if (st == -2 && (k & 1)) {
        for (int i = 0; i < n; ++i) s[i] = change(s[i]);
      }
      puts(s);
    } else {
      for (int i = n; i < 2 * n; ++i) {
        s[i] = s[i - n];
        a[i] = a[i - n];
      }
      for (int i = st, j = st;; i = j) {
        while (a[i + 1]) ++i;
        j = i + 1;
        while (!a[j]) ++j;
        int x = i + 1, y = j - 1, z = k;
        while (x <= y && z) {
          s[x] = s[i];
          s[y] = s[j];
          --z;
          ++x, --y;
        }
        if (z == 0 && (k & 1)) {
          for (int w = x; w <= y; ++w) s[w] = change(s[w]);
        }
        if (j >= st + n) break;
      }
      for (int i = 0; i < st; ++i) s[i] = s[i + n];
      s[n] = 0;
      puts(s);
    }
  }
}
