#include <bits/stdc++.h>
using namespace std;
const int N = 1e6 + 10;
int n, m;
int vis[N], l[N], r[N];
char s[N], ans[N];
queue<int> q;
template <typename T>
inline void chkmax(T &x, T y) {
  x = max(x, y);
}
template <typename T>
inline void chkmin(T &x, T y) {
  x = min(x, y);
}
template <typename T>
inline void read(T &x) {
  T f = 1;
  x = 0;
  char c = getchar();
  for (; !isdigit(c); c = getchar())
    if (c == '-') f = -f;
  for (; isdigit(c); c = getchar()) x = (x << 3) + (x << 1) + c - '0';
  x *= f;
}
int main() {
  scanf("%d%d%s", &n, &m, s + 1);
  memset(vis, 255, sizeof(vis));
  for (int i = 1; i <= n; ++i) l[i] = i - 1, r[i] = i + 1;
  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 u = q.front();
    q.pop();
    if (vis[l[u]] == -1) {
      vis[l[u]] = vis[u] + 1;
      q.push(l[u]);
    }
    if (vis[r[u]] == -1) {
      vis[r[u]] = vis[u] + 1;
      q.push(r[u]);
    }
  }
  for (int i = 1; i <= n; ++i) {
    if (vis[i] > m || vis[i] == -1) {
      if (m & 1)
        printf("%c", 'W' + 'B' - s[i]);
      else
        printf("%c", s[i]);
    } else {
      if (vis[i] & 1)
        printf("%c", 'W' + 'B' - s[i]);
      else
        printf("%c", s[i]);
    }
  }
  printf("\n");
  return 0;
}
