#include <bits/stdc++.h>
using namespace std;
int N, K;
string S;
char f[1001][2001];
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cin >> N >> K >> S;
  f[0][K] = '!';
  for (int(i) = (0); (i) < (int)(N); ++(i)) {
    char c = S[i];
    for (int j = 1; j < 2 * K; ++j)
      if (f[i][j]) {
        if (c == 'W') {
          f[i + 1][j + 1] = 'W';
        } else if (c == 'L') {
          f[i + 1][j - 1] = 'L';
        } else if (c == 'D') {
          f[i + 1][j] = 'D';
        } else {
          f[i + 1][j + 1] = 'W';
          f[i + 1][j - 1] = 'L';
          f[i + 1][j] = 'D';
        }
      }
  }
  int a = N, b = -1;
  if (f[a][0])
    b = 0;
  else if (f[a][2 * K])
    b = 2 * K;
  else {
    cout << "NO" << endl;
    return 0;
  }
  string X;
  for (; a > 0; --a) {
    char c = f[a][b];
    X += c;
    if (c == 'W')
      b--;
    else if (c == 'L')
      b++;
  }
  reverse((X).begin(), (X).end());
  cout << X << endl;
}
