#include <bits/stdc++.h>
using namespace std;
int n, k, cs[1005];
string s;
map<int, bool> dp[1005], vis[1005];
bool solve(int ind, int sum) {
  if (abs(sum) == k)
    if (ind == n)
      return true;
    else
      return false;
  if (ind == n) return false;
  bool &ref = dp[ind][sum];
  if (vis[ind][sum]) return ref;
  vis[ind][sum] = 1;
  if (s[ind] == 'W') {
    ref = solve(ind + 1, sum + 1);
    return ref;
  }
  if (s[ind] == 'L') {
    ref = solve(ind + 1, sum - 1);
    return ref;
  }
  if (s[ind] == 'D') {
    ref = solve(ind + 1, sum);
    return ref;
  }
  cs[ind] = 1;
  ref = solve(ind + 1, sum + 1);
  if (ref) return ref;
  cs[ind] = -1;
  ref = solve(ind + 1, sum - 1);
  if (ref) return ref;
  cs[ind] = 0;
  ref = solve(ind + 1, sum);
  return ref;
}
int main() {
  scanf("%d%d", &n, &k);
  cin >> s;
  for (int i = 0; i < n; i++) {
    if (s[i] == 'W')
      cs[i] = 1;
    else if (s[i] == 'L')
      cs[i] = -1;
    else if (s[i] == 'D')
      cs[i] = 0;
    else
      cs[i] = -100;
  }
  if (!solve(0, 0)) return puts("NO"), 0;
  for (int i = 0; i < n; i++)
    if (cs[i] == 1)
      printf("W");
    else if (cs[i] == -1)
      printf("L");
    else
      printf("D");
  printf("\n");
  return 0;
}
