#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1000000009;
long long POW(long long a, long long b, long long MMM = MOD) {
  long long ret = 1;
  for (; b; b >>= 1, a = (a * a) % MMM)
    if (b & 1) ret = (ret * a) % MMM;
  return ret;
}
long long gcd(long long a, long long b) { return b ? gcd(b, a % b) : a; }
long long lcm(long long a, long long b) {
  if (a == 0 || b == 0) return a + b;
  return a * (b / gcd(a, b));
}
int dx[] = {0, 1, 0, -1}, dy[] = {1, 0, -1, 0};
int ddx[] = {0, 0, 1, 1, 1, -1, -1, -1}, ddy[] = {1, -1, 1, 0, -1, 1, 0, -1};
int n, k;
char s[1001];
int d[1001][2001];
int go(int N, int K) {
  if (N == n) return (K == 1000 + k || K == 1000 - k);
  if ((K == 1000 + k) || (K == 1000 - k)) return 0;
  int &ret = d[N][K];
  if (ret != -1) return ret;
  ret = 0;
  if (s[N] == '?') {
    ret = max(ret, go(N + 1, K));
    ret = max(ret, go(N + 1, K - 1));
    ret = max(ret, go(N + 1, K + 1));
  } else if (s[N] == 'W')
    ret = max(ret, go(N + 1, K + 1));
  else if (s[N] == 'D')
    ret = max(ret, go(N + 1, K));
  else if (s[N] == 'L')
    ret = max(ret, go(N + 1, K - 1));
  return ret;
}
void track(int N, int K) {
  if (N == n) return;
  if (s[N] == '?') {
    if (go(N + 1, K + 1) == 1) {
      putchar('W');
      track(N + 1, K + 1);
    } else if (go(N + 1, K) == 1) {
      putchar('D');
      track(N + 1, K);
    } else if (go(N + 1, K - 1) == 1) {
      putchar('L');
      track(N + 1, K - 1);
    }
  } else if (s[N] == 'W')
    putchar('W'), track(N + 1, K + 1);
  else if (s[N] == 'D')
    putchar('D'), track(N + 1, K);
  else if (s[N] == 'L')
    putchar('L'), track(N + 1, K - 1);
}
int main() {
  memset(d, -1, sizeof(d));
  ;
  scanf("%d%d", &n, &k);
  scanf("%s", s);
  if (go(0, 1000) == 0)
    return !printf("NO");
  else
    track(0, 1000);
}
