#include <bits/stdc++.h>
using namespace std;
struct Debug {
  int cnt = 0;
  bool on = false;
  char debug[10] = "debug";
  template <class T>
  Debug& operator<<(const T& v) {
    if (on && cnt++ == 0) cerr << "debug: ";
    if (on) cerr << v << ' ';
    return *this;
  }
  Debug& operator<<(ostream& (*pManip)(ostream&)) {
    if (on) cerr << (*pManip);
    cnt = 0;
    return *this;
  }
} debug;
const int MAXN = 1e6 + 10;
int n, k;
string s, s0;
int main(int argc, char* argv[]) {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  if (argc > 1 && !strcmp(argv[1], debug.debug)) debug.on = true;
  cin >> n >> k;
  cin >> s0;
  s = s0 + s0 + s0;
  int i = 0, j = 0;
  for (; i < n; i++)
    if (s[i] == s[i + 1]) break;
  if (s[i] != s[i + 1]) {
    if (k % 2 == 0) {
      cout << s0 << endl;
      return 0;
    }
    for (auto& c : s0) c = 'W' + 'B' - c;
    cout << s0 << endl;
    return 0;
  }
  while (i < 3 * n) {
    while (i + 1 < 3 * n && s[i] == s[i + 1]) i++;
    j = i;
    while (j + 1 < 3 * n && s[j] != s[j + 1]) j++;
    if (j == 3 * n - 1) break;
    int kk;
    for (kk = 1; i + kk < j - kk && kk <= k; kk++) {
      s[i + kk] = s[i];
      s[j - kk] = s[j];
    }
    if (kk <= k) {
      if (i + kk == j - kk) s[i + kk] = s[i];
    } else if (k % 2) {
      for (int kkk = i + kk; kkk <= j - kk; kkk++) s[kkk] = 'W' + 'B' - s[kkk];
    }
    i = j + 1;
  }
  cout << s.substr(n, n) << endl;
  return 0;
}
