#include <bits/stdc++.h>
using namespace std;
long long power(long long a, long long b, long long m = 1000000007) {
  if (b == 0) return 1;
  if (b == 1) return a;
  long long res = power(a, b / 2, m);
  res = (res * res) % m;
  if (b & 1) res = (res * a) % m;
  return res;
}
long long modinv(long long a, long long m = 1000000007) {
  return power(a, m - 2, m);
}
long long add(long long a, long long b, long long m = 1000000007) {
  long long c = (a % m + b % m);
  if (c >= m) c -= m;
  return c;
}
long long sub(long long a, long long b, long long m = 1000000007) {
  long long c = (a % m - b % m);
  if (c < 0) c += m;
  return c;
}
long long mul(long long a, long long b, long long m = 1000000007) {
  return (a * b) % m;
}
string ans = "NO", s, s1;
long long n, k;
long long dp[1005][2 * 1005];
bool fun(long long idx, long long val) {
  if (idx == n) {
    dp[idx][val + 1005] = (abs(val) == k);
    return abs(val) == k;
  }
  if (abs(val) == k) return 0;
  long long &ans = dp[idx][val + 1005];
  if (ans != -1) return ans;
  ans = 0;
  if (s[idx] == 'W' || s[idx] == '?') ans |= fun(idx + 1, val + 1);
  if (s[idx] == 'L' || s[idx] == '?') ans |= fun(idx + 1, val - 1);
  if (s[idx] == 'D' || s[idx] == '?') ans |= fun(idx + 1, val);
  return ans;
}
long long find(char c) {
  if (c == 'D') return 0;
  if (c == 'W') return 1;
  return -1;
}
void print(long long idx, long long val) {
  if (idx == n) {
    cout << "\n";
    return;
  }
  if (s[idx] == 'L' || s[idx] == 'D' || s[idx] == 'W') {
    cout << s[idx];
    print(idx + 1, val + find(s[idx]));
  } else if (dp[idx + 1][val - 1 + 1005] == 1) {
    cout << "L";
    print(idx + 1, val - 1);
  } else if (dp[idx + 1][val + 1 + 1005] == 1) {
    cout << "W";
    print(idx + 1, val + 1);
  } else {
    cout << "D";
    print(idx + 1, val);
  }
}
void solve() {
  cin >> n >> k >> s;
  memset(dp, -1, sizeof(dp));
  if (fun(0, 0))
    print(0, 0);
  else
    cout << "NO"
         << "\n";
}
int32_t main() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  cout.tie(NULL);
  long long t = 1;
  for (long long i = 1; i <= t; i++) {
    solve();
  }
  return 0;
}
