#include <bits/stdc++.h>
using namespace std;
inline int read() {
  int f = 1, ans = 0;
  char c = getchar();
  while (c < '0' || c > '9') {
    if (c == '-') f = -1;
    c = getchar();
  }
  while (c >= '0' && c <= '9') {
    ans = ans * 10 + c - '0';
    c = getchar();
  }
  return f * ans;
}
const int MAXN = 4000001;
char str[MAXN];
int n, k, A[MAXN], B[MAXN], C[MAXN];
void print(int opt) { opt ? printf("W") : printf("B"); }
int main() {
  n = read(), k = read();
  scanf("%s", str + 1);
  for (int i = 1; i <= n; i++) A[i] = (str[i] == 'W');
  A[0] = A[n], A[n + 1] = A[1];
  for (int i = 1; i <= n; i++)
    B[i] = (A[i - 1] == A[i] || A[i] == A[i + 1]), B[i + n] = B[i];
  bool F = 0;
  for (int i = 1; i <= n; i++) F |= B[i];
  if (!F) {
    for (int i = 1; i <= n; i++) print(A[i] ^ (k & 1));
    printf("\n");
    return 0;
  }
  int ps = 1;
  for (int i = 1; i <= n; i++)
    if (B[i]) ps = i;
  for (int i = n + 1; i <= 2 * n; i++) {
    if (B[i]) ps = i;
    C[i - n] = i - ps;
  }
  for (int i = 2 * n; i > n; i--)
    if (B[i]) ps = i;
  for (int i = n; i >= 1; i--) {
    if (B[i]) ps = i;
    C[i] = min(C[i], ps - i);
  }
  for (int i = 1; i <= n; i++) {
    if (B[i])
      print(A[i]);
    else
      print(A[i] ^ (min(k, C[i]) & 1));
  }
  printf("\n");
  return 0;
}
