#include <bits/stdc++.h>
using namespace std;
const long long mod = 1e9 + 7;
const int maxn = 3e5 + 100;
long long n, m, k, t;
char a[maxn];
int b[maxn];
bool f[maxn];
queue<int> q, q1;
int main() {
  scanf("%lld%lld%s", &n, &m, a + 1);
  a[0] = a[n];
  a[n + 1] = a[1];
  for (int i = 1; i <= n; i++) {
    b[i] = -1;
    if (a[i] == a[i - 1] || a[i] == a[i + 1]) q.push(i), q1.push(0), f[i] = 1;
  }
  while (!q.empty()) {
    int now = q.front(), now2 = q1.front();
    b[now] = now2;
    q.pop();
    q1.pop();
    if (!f[now - 1] && now > 1) {
      q.push(now - 1);
      q1.push(now2 + 1);
      f[now - 1] = 1;
    } else if (now == 1 && !f[n]) {
      q.push(n);
      q1.push(now2 + 1);
      f[n] = 1;
    }
    if (!f[now + 1] && now < n) {
      q.push(now + 1);
      q1.push(now2 + 1);
      f[now + 1] = 1;
    } else if (now == n && !f[1]) {
      q.push(1);
      q1.push(now2 + 1);
      f[1] = 1;
    }
  }
  for (int i = 1; i <= n; i++) {
    if (b[i] == -1 || b[i] >= m) {
      if (m & 1) {
        if (a[i] == 'W')
          printf("B");
        else
          printf("W");
      } else
        printf("%c", a[i]);
    } else {
      if (b[i] & 1) {
        if (a[i] == 'W')
          printf("B");
        else
          printf("W");
      } else
        printf("%c", a[i]);
    }
  }
  cout << endl;
}
