#include <bits/stdc++.h>
using namespace std;
int n, k;
int pr(int i) { return (i - 1 + n) % n; }
int nx(int i) { return (i + 1) % n; }
int get(int i, int j) {
  if (i > j) swap(i, j);
  return min(j - i, n - j + i);
}
char no(char el) {
  if (el == 'B')
    return 'W';
  else
    return 'B';
}
int gg(string s) {
  int b = 1;
  for (char i : s) {
    if (i != 'B') b = 0;
  }
  int w = 1;
  for (char i : s) {
    if (i != 'W') w = 0;
  }
  return max(w, b);
}
signed main() {
  string s;
  cin >> n >> k >> s;
  if (gg(s)) {
    cout << s;
    return 0;
  }
  vector<int> used(n, 0);
  int l = 0, r = 0, op = 1e6;
  bool ch = false;
  while (l < n && op > 0) {
    --op;
    if (used[l]) {
      ++l;
    } else if (s[l] == s[pr(l)]) {
      ch = true;
      while (s[l] == s[nx(l)]) used[l] = 1, l = nx(l);
      r = nx(l);
      while (s[r] != s[nx(r)]) used[r] = 1, r = nx(r);
      int cr = r;
      while (s[nx(cr)] == s[cr]) used[cr] = 1, cr = nx(cr);
      char last = s[l];
      for (int i = nx(l); i != r; i = nx(i)) {
        if (get(l, i) > k && get(r, i) > k)
          s[i] = no(last), last = no(last);
        else if (get(l, i) < get(r, i))
          s[i] = s[l], last = s[l];
        else if (get(l, i) >= get(r, i))
          s[i] = s[r], last = s[r];
      }
      ++l;
    } else {
      ++l;
    }
  }
  if (!ch) {
    if (k % 2 == 0)
      cout << s;
    else
      for (char i : s) cout << no(i);
    return 0;
  }
  cout << s;
}
