#include <bits/stdc++.h>
using namespace std;
int n, k, is[678901], t[678901], ti;
char s[678901];
queue<int> tp, tp2;
int main() {
  scanf("%d%d%s", &n, &k, s + 1);
  for (int i = 1; i <= n; i++)
    if (s[i] == s[i == 1 ? n : i - 1])
      is[i] = is[i == 1 ? n : i - 1] = (s[i] == 'B' ? 1 : 2), tp.push(i),
      tp.push(i == 1 ? n : i - 1);
  for (int i = 1; i <= k; i++) {
    if (tp.empty()) break;
    ti++;
    while (!tp.empty()) {
      int s1 = tp.front();
      tp.pop();
      int lb = s1 == 1 ? n : s1 - 1, rb = s1 == n ? 1 : s1 + 1;
      if (!is[lb]) {
        is[lb] = is[s1];
        t[lb] = ti;
        tp2.push(lb);
      } else if (t[lb] == ti) {
        if ((is[s1] == 1 && ((s[lb] == 'B' && ti % 2 == 1) ||
                             (s[lb] == 'W' && ti % 2 == 0))) ||
            (is[s1] == 0 &&
             ((s[lb] == 'B' && ti % 2 == 0) || (s[lb] == 'W' && ti % 2 == 1))))
          is[lb] = is[s1];
      }
      if (!is[rb]) {
        is[rb] = is[s1];
        t[rb] = ti;
        tp2.push(rb);
      } else if (t[rb] == ti) {
        if ((is[s1] == 1 && ((s[rb] == 'B' && ti % 2 == 1) ||
                             (s[rb] == 'W' && ti % 2 == 0))) ||
            (is[s1] == 0 &&
             ((s[rb] == 'B' && ti % 2 == 0) || (s[rb] == 'W' && ti % 2 == 1))))
          is[rb] = is[s1];
      }
    }
    while (!tp2.empty()) tp.push(tp2.front()), tp2.pop();
  }
  for (int i = 1; i <= n; i++)
    if (is[i])
      printf("%c", is[i] == 1 ? 'B' : 'W');
    else
      printf("%c", ((s[i] == 'B') ^ (k & 1)) ? 'B' : 'W');
}
