#include <bits/stdc++.h>
#pragma GCC optimize(3)
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#pragma comment(linker, "/stack:200000000")
using namespace std;
void io() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
}
inline long long __gcd(long long a, long long b) {
  return b == 0 ? a : __gcd(b, a % b);
}
inline void exgcd(long long a, long long b, long long& x, long long& y) {
  if (!b)
    x = 1, y = 0;
  else
    exgcd(b, a % b, y, x), y -= a / b * x;
}
int n, t, x, k, cnt = 1;
int vis[500100];
int a[500100], l[500100], r[500100];
char s[500100], tp[500100];
queue<int> q;
int main() {
  io();
  cin >> n >> k >> (s + 1);
  for (int i = 0; i <= n; ++i) vis[i] = -1;
  for (int i = 1; i <= n; ++i) l[i] = i - 1, r[i] = i + 1, tp[i] = s[i];
  l[1] = n;
  r[n] = 1;
  for (int i = 1; i <= n; ++i)
    if (s[l[i]] == s[i] || s[r[i]] == s[i]) vis[i] = 0, q.push(i);
  while (!q.empty()) {
    int top = q.front();
    q.pop();
    if (vis[l[top]] == -1) vis[l[top]] = vis[top] + 1, q.push(l[top]);
    if (vis[r[top]] == -1) vis[r[top]] = vis[top] + 1, q.push(r[top]);
  }
  for (int i = 1; i <= n; ++i) {
    if (vis[i] == -1 || vis[i] > k) {
      if (k & 1) {
        if (s[i] == 'B')
          cout << 'W';
        else
          cout << 'B';
      } else
        cout << s[i];
    } else {
      if (vis[i] & 1) {
        if (s[i] == 'B')
          cout << 'W';
        else
          cout << 'B';
      } else
        cout << s[i];
    }
  }
}
