#include <bits/stdc++.h>
using namespace std;
using ii = pair<int, int>;
const int N = 2e5 + 5;
int n, k;
char c[3 * N];
vector<ii> blks;
inline char toggle(char x) { return (x == 'W') ? 'B' : 'W'; }
int main() {
  ios::sync_with_stdio(0);
  cout.tie(0);
  cin.tie(0);
  cin >> n >> k;
  for (int i = 1; i <= n; ++i) {
    cin >> c[i];
    c[i + n] = c[i + 2 * n] = c[i];
  }
  char prec = 'X';
  int pl = 0, cnt = 0;
  for (int i = 1; i <= 3 * n + 1; ++i) {
    if (c[i] != prec) {
      if (cnt > 1) blks.emplace_back(pl, i - 1);
      cnt = 0;
      pl = i;
    }
    prec = c[i];
    ++cnt;
  }
  if (blks.size() == 0) {
    k %= 2;
    if (k)
      for (int i = 1; i <= n; ++i) c[i] = toggle(c[i]);
    for (int i = 1; i <= n; ++i) cout << c[i];
    return 0;
  }
  for (int z = 0; z + 1 < (int)blks.size(); ++z) {
    int l = blks[z].second, r = blks[z + 1].first;
    if (c[l] == c[r]) {
      for (int i = l + 1; i < r; ++i) {
        int d = min(i - l, r - i);
        if (k >= d)
          c[i] = c[l];
        else if (k & 1)
          c[i] = toggle(c[i]);
      }
    } else {
      for (int i = l + 1; i < r; ++i) {
        int d = min(i - l, r - i);
        if (k >= d) {
          if (i <= ((l + r) / 2))
            c[i] = c[l];
          else
            c[i] = c[r];
        } else if (k & 1)
          c[i] = toggle(c[i]);
      }
    }
  }
  for (int i = n + 1; i <= 2 * n; ++i) cout << c[i];
  return 0;
}
