#include <bits/stdc++.h>
using namespace std;
int n, k, cl, dem, vt, vtc;
char x;
int a[300001];
int b[300001];
int F[300001];
int cd[300001];
int main() {
  ios_base::sync_with_stdio(false);
  cin >> n >> k;
  for (int i = 1; i <= n; i++) {
    cin >> x;
    if (x == 'B')
      a[i] = 1;
    else
      a[i] = 0;
  }
  a[0] = a[n];
  for (int i = 1; i <= n; i++)
    if (a[i] == a[i - 1]) cd[i] = cd[i - 1] = 1;
  if (a[1] == a[n]) cd[1] = cd[n] = 1;
  for (int i = 1; i <= n; i++)
    if (cd[i] == 1)
      F[i] = 0;
    else
      F[i] = 1e9 + 100000;
  vt = -1;
  for (int i = 1; i <= n; i++)
    if (cd[i] == 1) {
      vt = i;
      break;
    }
  if (vt != -1) {
    vtc = vt;
    cl = a[vt];
    b[vt] = a[vt];
    vt = (vt % (n)) + 1;
    while (vt != vtc) {
      if (cd[vt] == 1) {
        dem = 0;
        cl = a[vt];
        vt = (vt % (n)) + 1;
        continue;
      }
      dem++;
      if (F[vt] > dem) {
        F[vt] = dem;
        b[vt] = cl;
      }
      vt = (vt % (n)) + 1;
    }
    vt = vtc;
    cl = a[vt];
    b[vt] = a[vt];
    vt = vt - 1;
    if (vt == 0) vt = n;
    dem = 0;
    while (vt != vtc) {
      if (cd[vt] == 1) {
        dem = 0;
        cl = a[vt];
        b[vt] = a[vt];
        vt = vt - 1;
        if (vt == 0) vt = n;
        continue;
      }
      dem++;
      if (F[vt] > dem) {
        F[vt] = dem;
        b[vt] = cl;
      }
      vt = vt - 1;
      if (vt == 0) vt = n;
    }
  }
  for (int i = 1; i <= n; i++)
    if (F[i] <= k) {
      if (b[i] == 0)
        putchar('W');
      else
        putchar('B');
    } else if ((a[i] + (k % 2)) % 2 == 0)
      putchar('W');
    else
      putchar('B');
  return 0;
}
