#include <bits/stdc++.h>
using namespace std;
long long dp[2010][2010], pre[2010][2010];
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  int base = 1000;
  long long n, k;
  cin >> n >> k;
  string s;
  cin >> s;
  dp[0][base + 0] = 1;
  for (int i = 1; i <= n; ++i)
    for (int j = 0; j < 2010; ++j) {
      if (s[i - 1] == 'L') {
        if (base - k < j + 1 and j + 1 < base + k)
          dp[i][j] |= dp[i - 1][j + 1], pre[i][j] = j + 1;
      } else if (s[i - 1] == 'W') {
        if (base - k < j - 1 and j - 1 < base + k)
          dp[i][j] |= dp[i - 1][j - 1], pre[i][j] = j - 1;
      } else if (s[i - 1] == 'D') {
        if (base - k < j and j < base + k)
          dp[i][j] |= dp[i - 1][j], pre[i][j] = j;
      } else {
        if (base - k < j + 1 and j + 1 < base + k and dp[i - 1][j + 1])
          dp[i][j] |= dp[i - 1][j + 1], pre[i][j] = j + 1;
        else if (base - k < j - 1 and j - 1 < base + k and dp[i - 1][j - 1])
          dp[i][j] |= dp[i - 1][j - 1], pre[i][j] = j - 1;
        else if (base - k < j and j < base + k and dp[i - 1][j]) {
          dp[i][j] = dp[i - 1][j], pre[i][j] = j;
        }
      }
    }
  string ans;
  function<void(int, int)> back = [&](int n, int k) {
    if (n == 0) return;
    int nxt = pre[n][k];
    if (nxt == k - 1)
      ans.push_back('W');
    else if (nxt == k + 1)
      ans.push_back('L');
    else if (nxt == k)
      ans.push_back('D');
    assert(dp[n][k]);
    return back(n - 1, nxt);
  };
  if (dp[n][base - k])
    back(n, base - k);
  else if (dp[n][base + k])
    back(n, base + k);
  else
    return cout << "NO\n", 0;
  reverse(ans.begin(), ans.end());
  cout << ans << '\n';
}
