#include <bits/stdc++.h>
using namespace std;
const int maxn = 1005;
char s[maxn], ans[maxn];
bool d[maxn][4 * maxn];
int main() {
  int n, k;
  while (~scanf("%d%d", &n, &k)) {
    scanf("%s", s + 1);
    int mid = 2000;
    memset(d, 0, sizeof(d));
    d[0][mid] = 1;
    for (int i = 1; i <= n; i++) {
      for (int j = mid - k; j <= mid + k; j++) {
        if (i != n && (j == mid - k || j == mid + k)) continue;
        if (s[i] == 'D')
          d[i][j] = d[i - 1][j];
        else if (s[i] == 'W')
          d[i][j] = d[i - 1][j - 1];
        else if (s[i] == 'L')
          d[i][j] = d[i - 1][j + 1];
        else
          d[i][j] = max(max(d[i - 1][j - 1], d[i - 1][j + 1]), d[i - 1][j]);
      }
    }
    if (!d[n][mid - k] && !d[n][mid + k]) {
      printf("NO\n");
      continue;
    }
    if (d[n][mid - k]) {
      int tmp = mid - k;
      ans[n + 1] = 0;
      for (int i = n; i >= 1; i--) {
        if (s[i] != '?') {
          ans[i] = s[i];
          if (s[i] == 'L')
            tmp++;
          else if (s[i] == 'W')
            tmp--;
        } else {
          if (d[i - 1][tmp] && tmp != mid - k && tmp != mid + k)
            ans[i] = 'D';
          else if (d[i - 1][tmp + 1] && tmp + 1 > mid - k &&
                   tmp + 1 < mid + k) {
            ans[i] = 'L';
            tmp++;
          } else if (d[i - 1][tmp - 1] && tmp - 1 > mid - k &&
                     tmp - 1 < mid + k) {
            ans[i] = 'W';
            tmp--;
          }
        }
      }
      printf("%s\n", ans + 1);
      continue;
    }
    if (d[n][mid + k]) {
      int tmp = mid + k;
      ans[n + 1] = 0;
      for (int i = n; i >= 1; i--) {
        if (s[i] == 'L' || s[i] == 'W' || s[i] == 'D') {
          ans[i] = s[i];
          if (s[i] == 'L')
            tmp++;
          else if (s[i] == 'W')
            tmp--;
        } else {
          if (d[i - 1][tmp] && tmp != mid - k && tmp != mid + k)
            ans[i] = 'D';
          else if (d[i - 1][tmp + 1] && tmp + 1 > mid - k &&
                   tmp + 1 < mid + k) {
            ans[i] = 'L';
            tmp++;
          } else if (d[i - 1][tmp - 1] && tmp - 1 > mid - k &&
                     tmp - 1 < mid + k) {
            ans[i] = 'W';
            tmp--;
          }
        }
      }
      printf("%s\n", ans + 1);
    }
  }
  return 0;
}
