#include <bits/stdc++.h>
using namespace std;
const int MAX_N = 200200;
int n, k;
string second;
bool block[MAX_N];
pair<int, char> distBlock[MAX_N];
char to(char k) { return (k == '0') ? 'W' : 'B'; }
char notto(char k) { return (k == '0') ? 'B' : 'W'; }
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cin >> n >> k >> second;
  for (int i = 0; i < n; i++) second[i] = (second[i] == 'B') ? '1' : '0';
  for (int i = 0; i < n; i++)
    if (second[i] == second[(i + n - 1) % n] ||
        second[i] == second[(i + 1) % n])
      block[i] = 1;
  for (int i = 0; i < n; i++) distBlock[i] = make_pair(1e9 + 5, '?');
  for (int i = 0; i < n; i++)
    if (block[i] && !block[(i + 1) % n]) {
      int cur = (i + 1) % n;
      int d = 1;
      char val = second[i];
      while (!block[cur]) {
        distBlock[cur] = min(distBlock[cur], make_pair(d, val));
        cur++;
        if (cur == n) cur = 0;
        d++;
      }
    }
  for (int i = 0; i < n; i++)
    if (block[i] && !block[(i + n - 1) % n]) {
      int cur = (i + n - 1) % n;
      int d = 1;
      char val = second[i];
      while (!block[cur]) {
        distBlock[cur] = min(distBlock[cur], make_pair(d, val));
        cur--;
        if (cur == -1) cur = n - 1;
        d++;
      }
    }
  for (int i = 0; i < n; i++)
    ;
  string ans = "";
  for (int i = 0; i < n; i++) {
    if (block[i])
      ans += to(second[i]);
    else {
      if (distBlock[i].first <= k)
        ans += to(distBlock[i].second);
      else {
        if (k % 2 == 0)
          ans += to(second[i]);
        else
          ans += notto(second[i]);
      }
    }
  }
  cout << ans << "\n";
}
