#include <bits/stdc++.h>
using namespace std;
const long long infl = 1e5 + 5;
long long int m, n, q, x, y, k, mx = -1, mn = infl, f, val, sz, sm, cnt, t = 1,
                                i, j, ind = -1;
long long int dp[2004][2004];
string s;
std::map<pair<long long int, long long int>,
         pair<long long int, long long int> >
    nxt;
std::map<pair<long long int, long long int>, char> ans;
int rec(int ind, int st) {
  if (ind == n) {
    if (abs(1001 - st) == k) return 0;
    return infl;
  }
  if (abs(1001 - st) >= k) return infl;
  if (dp[ind][st] != -1) {
    return dp[ind][st];
  }
  long long int re = 0;
  if (s[ind] == 'D') {
    re = rec(ind + 1, st);
    nxt[make_pair(ind, st)] = make_pair(ind + 1, st);
    ans[make_pair(ind, st)] = 'D';
  } else if (s[ind] == 'L') {
    re = rec(ind + 1, st - 1);
    nxt[make_pair(ind, st)] = make_pair(ind + 1, st - 1);
    ans[make_pair(ind, st)] = 'L';
  } else if (s[ind] == 'W') {
    re = rec(ind + 1, st + 1);
    nxt[make_pair(ind, st)] = make_pair(ind + 1, st + 1);
    ans[make_pair(ind, st)] = 'W';
  } else {
    int tmp, tmp1;
    tmp = rec(ind + 1, st + 1);
    tmp1 = rec(ind + 1, st - 1);
    if (tmp < tmp1) {
      re = tmp;
      nxt[make_pair(ind, st)] = make_pair(ind + 1, st + 1);
      ans[make_pair(ind, st)] = 'W';
    } else {
      re = tmp1;
      nxt[make_pair(ind, st)] = make_pair(ind + 1, st - 1);
      ans[make_pair(ind, st)] = 'L';
    }
    tmp = rec(ind + 1, st);
    if (tmp < re) {
      re = tmp;
      nxt[make_pair(ind, st)] = make_pair(ind + 1, st);
      ans[make_pair(ind, st)] = 'D';
    }
  }
  dp[ind][st] = re;
  return re;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  if (fopen("inp.txt", "r")) {
    freopen("myfile.txt", "w", stdout);
    freopen("inp.txt", "r", stdin);
  }
  cin >> n >> k;
  cin >> s;
  for (i = 0; i < 2004; i++) {
    for (j = 0; j < 2004; j++) {
      dp[i][j] = -1;
    }
  }
  sm = rec(0, 1001);
  if (sm != 0) {
    cout << "NO";
    return 0;
  }
  pair<long long int, long long int> p = make_pair(0, 1001);
  while (p.first != n) {
    cout << ans[p];
    p = nxt[p];
  }
  return 0;
}
