#include <bits/stdc++.h>
using namespace std;
const int Maxn = 200005;
int n, k;
char str[Maxn];
map<int, char> stable;
char res[Maxn];
vector<int> quer;
char Not(char ch) { return ch == 'B' ? 'W' : 'B'; }
int main() {
  scanf("%d %d", &n, &k);
  scanf("%s", str);
  for (int i = 0; i < n; i++) {
    int pi = (i + n - 1) % n;
    int ni = (i + 1) % n;
    if (str[i] == str[pi] || str[i] == str[ni]) {
      stable[i] = str[i];
      stable[i - n] = str[i];
      stable[i + n] = str[i];
      res[i] = str[i];
    } else
      quer.push_back(i);
  }
  for (int i = 0; i < quer.size(); i++) {
    char my = k % 2 == 0 ? str[quer[i]] : Not(str[quer[i]]);
    if (!stable.empty()) {
      map<int, char>::iterator it2 = stable.upper_bound(quer[i]);
      auto it1 = it2;
      it1--;
      int got = min(quer[i] - it1->first, it2->first - quer[i]);
      if (got <= k)
        if (quer[i] - it1->first == got)
          my = it1->second;
        else
          my = it2->second;
    }
    res[quer[i]] = my;
  }
  res[n] = '\0';
  printf("%s\n", res);
  return 0;
}
