#include <bits/stdc++.h>
using namespace std;
template <class T>
inline T sqr(T x) {
  return x * x;
}
template <class T>
inline string tostr(const T &x) {
  stringstream ss;
  ss << x;
  return ss.str();
}
inline long long parse(const string &s) {
  stringstream ss(s);
  long long x;
  ss >> x;
  return x;
}
const double EPS = 1e-12;
const int INF = 1000 * 1000 * 1000;
const long long LINF = INF * 1ll * INF;
const double DINF = 1e200;
const double PI = 3.1415926535897932384626433832795l;
int gcd(int a, int b) { return a ? gcd(b % a, a) : b; }
long long gcd(long long a, long long b) { return a ? gcd(b % a, a) : b; }
long long gcdex(long long a, long long b, long long &x, long long &y) {
  if (!a) {
    x = 0, y = 1;
    return b;
  }
  long long k = b / a;
  long long g = gcdex(b - k * a, a, y, x);
  x -= k * y;
  return g;
}
long long inv(long long a, long long m) {
  long long x, y, g;
  g = gcdex(a, m, x, y);
  return (x % (m / g) + m / g) % m / g;
}
long long crt(long long a1, long long m1, long long a2, long long m2) {
  long long a = (a2 - a1 % m2 + m2) % m2;
  long long x, y, g;
  g = gcdex(m1, m2, x, y);
  if (a % g) return -1;
  long long m = m1 / g * m2;
  x *= a / g;
  x = (x % m2 + m2) % m2;
  long long r = (a1 + x * m1) % m;
  assert(r % m1 == a1 && r % m2 == a2);
  return r;
}
long long powmod(long long a, long long p, long long m) {
  long long r = 1;
  while (p) {
    if (p & 1) r = r * a % m;
    p >>= 1;
    a = a * a % m;
  }
  return r;
}
bool isprime(long long a) {
  if (a <= 1) return false;
  for (long long i = 2; i * i <= a; ++i) {
    if (a % i == 0) return false;
  }
  return true;
}
long long sqrtup(long long a) {
  if (!a) return 0;
  long long x = max(0ll, (long long)sqrt((double)a));
  while (x * x >= a) --x;
  while ((x + 1) * (x + 1) < a) ++x;
  return x + 1;
}
long long isqrt(long long a) {
  long long x = max(0ll, (long long)sqrt((double)a));
  while (x * x > a) --x;
  while ((x + 1) * (x + 1) <= a) ++x;
  return x;
}
long long sgn(long long x) { return x < 0 ? -1 : x > 0 ? 1 : 0; }
template <class T>
ostream &operator<<(ostream &s, const vector<T> &v);
template <class A, class B>
ostream &operator<<(ostream &s, const pair<A, B> &p);
template <class K, class V>
ostream &operator<<(ostream &s, const map<K, V> &m);
template <class T, size_t N>
ostream &operator<<(ostream &s, const array<T, N> &a);
template <class... T>
ostream &operator<<(ostream &s, const tuple<T...> &t);
template <class T>
ostream &operator<<(ostream &s, const vector<T> &v) {
  s << '[';
  for (int i = 0; i < (((int)(v).size())); ++i) {
    if (i) s << ',';
    s << v[i];
  }
  s << ']';
  return s;
}
template <class A, class B>
ostream &operator<<(ostream &s, const pair<A, B> &p) {
  s << "(" << p.first << "," << p.second << ")";
  return s;
}
template <class K, class V>
ostream &operator<<(ostream &s, const map<K, V> &m) {
  s << "{";
  bool f = false;
  for (const auto &it : m) {
    if (f) s << ",";
    f = true;
    s << it.first << ": " << it.second;
  }
  s << "}";
  return s;
}
template <class T>
ostream &operator<<(ostream &s, const set<T> &m) {
  s << "{";
  bool f = false;
  for (const auto &it : m) {
    if (f) s << ",";
    f = true;
    s << it;
  }
  s << "}";
  return s;
}
template <class T>
ostream &operator<<(ostream &s, const multiset<T> &m) {
  s << "{";
  bool f = false;
  for (const auto &it : m) {
    if (f) s << ",";
    f = true;
    s << it;
  }
  s << "}";
  return s;
}
template <class T, size_t N>
ostream &operator<<(ostream &s, const array<T, N> &a) {
  s << '[';
  for (int i = 0; i < (((int)(a).size())); ++i) {
    if (i) s << ',';
    s << a[i];
  }
  s << ']';
  return s;
}
template <size_t n, class... T>
struct put1 {
  static ostream &put(ostream &s, const tuple<T...> &t) {
    s << get<sizeof...(T) - n>(t);
    if (n > 1) s << ',';
    return put1<n - 1, T...>::put(s, t);
  }
};
template <class... T>
struct put1<0, T...> {
  static ostream &put(ostream &s, const tuple<T...> &t) { return s; }
};
template <class... T>
ostream &operator<<(ostream &s, const tuple<T...> &t) {
  s << "(";
  put1<sizeof...(T), T...>::put(s, t);
  s << ")";
  return s;
}
ostream &put2(ostream &s, const tuple<> &t) { return s; }
template <class U>
ostream &put2(ostream &s, const tuple<U> &t) {
  return s << get<0>(t);
}
template <class U, class V, class... T>
ostream &put2(ostream &s, const tuple<U, V, T...> &t) {
  return s << t;
}
void nope() {
  cout << "no";
  exit(0);
}
int main(int argc, char **argv) {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.precision(20);
  int n, m;
  cin >> m >> n;
  vector<int> A(m);
  int s = 0;
  for (int i = 0; i < (n); ++i) {
    cin >> A[i];
    A[i] -= m - 1;
    s += A[i];
  }
  if (s < 0) nope();
  if (n == m && s) nope();
  if (s) {
    int t = s;
    for (int i = m - s % (m - n); i < m; ++i) {
      A[i] = -s / (m - n) - 1;
      t += A[i];
    }
    for (int i = n; i < m - s % (m - n); ++i) {
      A[i] = -s / (m - n);
      t += A[i];
    }
    assert(!t);
  }
  do {
  } while (false);
  for (int i = 0; i < (m - 1); ++i) {
    if (A[i + 1] > A[i]) nope();
  }
  vector<string> R(m, string(m, 'X'));
  for (int i = 0; i < (m); ++i) {
    for (int j = 0; j < (m); ++j) {
      if (i == j)
        R[i][j] = 'X';
      else
        R[i][j] = 'D';
    }
  }
  priority_queue<pair<int, int> > qu;
  for (int i = 0; i < (m); ++i) {
    qu.push(make_pair(-A[i], i));
  }
  auto need = [](bool f) {
    if (!f) nope();
  };
  for (int i = 0; i < (m); ++i) {
    do {
    } while (false);
    vector<pair<int, int> > v;
    while (A[i] > 0) {
      need(!qu.empty());
      pair<int, int> p = qu.top();
      qu.pop();
      do {
      } while (false);
      if (-p.first != A[p.second]) continue;
      if (p.second == i || R[i][p.second] != 'D') {
        v.push_back(p);
        continue;
      }
      R[i][p.second] = 'W';
      R[p.second][i] = 'L';
      --A[i];
      ++A[p.second];
      --p.first;
      assert(p.first == -A[p.second]);
      v.push_back(p);
    }
    for (pair<int, int> p : v) qu.push(p);
  }
  for (int i = 0; i < (m); ++i) {
    assert(!A[i]);
  }
  cout << "yes\n";
  for (int i = 0; i < (((int)(R).size())); ++i) cout << R[i] << '\n';
  ;
  return 0;
}
