#include <bits/stdc++.h>
using namespace std;
const int N = 1234;
int f[N][N + N];
int n, k;
char in[N];
char res[N];
bool solve(int i, int d) {
  if (i == n) return (abs(N - d) == k);
  if (abs(d - N) == k) return 0;
  if (f[i][d] != -1) return f[i][d];
  if (in[i] != '?') {
    int pl = 0;
    if (in[i] == 'W') pl = 1;
    if (in[i] == 'L') pl = -1;
    if (solve(i + 1, d + pl)) {
      res[i] = in[i];
      return f[i][d] = 1;
    }
  } else {
    if (solve(i + 1, d)) {
      res[i] = 'D';
      return f[i][d] = 1;
    }
    if (solve(i + 1, d + 1)) {
      res[i] = 'W';
      return f[i][d] = 1;
    }
    if (solve(i + 1, d - 1)) {
      res[i] = 'L';
      return f[i][d] = 1;
    }
  }
  return f[i][d] = 0;
}
int main() {
  scanf("%d %d %s", &n, &k, &in);
  memset(f, -1, sizeof f);
  if (!solve(0, N)) {
    puts("NO");
  } else {
    printf("%s", res);
  }
  return 0;
}
