#include <bits/stdc++.h>
using namespace std;
const double pi = acos(-1);
int dx[] = {0, 0, 1, -1, 1, 1, -1, -1};
int dy[] = {1, -1, 0, 0, -1, 1, 1, -1};
const int N = 1005;
int n, Ak, memo[N][2 * N];
string s;
int solve(int i = 0, int k = 0) {
  if (i == n) return (k == Ak || k == -Ak);
  if (k >= Ak || k <= -Ak) return 0;
  int &ret = memo[i][k + N];
  if (~ret) return ret;
  ret = 0;
  if (s[i] == 'W')
    ret = solve(i + 1, k + 1);
  else if (s[i] == 'L')
    ret = solve(i + 1, k - 1);
  else if (s[i] == 'D')
    ret = solve(i + 1, k);
  else {
    ret = solve(i + 1, k + 1);
    if (ret) return ret;
    ret = solve(i + 1, k - 1);
    if (ret) return ret;
    ret = solve(i + 1, k);
  }
  return ret;
}
void printpath(int i = 0, int k = 0) {
  if (i == n) return;
  if (s[i] == 'W' && solve(i + 1, k + 1)) {
    cout << 'W';
    printpath(i + 1, k + 1);
  } else if (s[i] == 'L' && solve(i + 1, k - 1)) {
    cout << 'L';
    printpath(i + 1, k - 1);
  } else if (s[i] == 'D' && solve(i + 1, k)) {
    cout << 'D';
    printpath(i + 1, k);
  } else {
    if (solve(i + 1, k + 1)) {
      cout << 'W';
      printpath(i + 1, k + 1);
    } else if (solve(i + 1, k - 1)) {
      cout << 'L';
      printpath(i + 1, k - 1);
    } else if (solve(i + 1, k)) {
      cout << 'D';
      printpath(i + 1, k);
    }
  }
}
int main() {
  cin >> n >> Ak >> s;
  memset(memo, -1, sizeof memo);
  if (solve())
    printpath();
  else
    puts("NO");
}
