#include <bits/stdc++.h>
using namespace std;
int main() {
  vector<pair<string, bool> > v(50);
  string s;
  for (int i = 0; i < 26; i++) {
    v[i].first = (char)(65 + i);
    v[i].second = false;
  }
  for (int i = 26; i < 50; i++) {
    v[i].first = "A";
    v[i].first += (char)(97 + i - 26);
    v[i].second = false;
  }
  int n, k;
  cin >> n >> k;
  for (int i = 0; i < n - k + 1; i++) {
    cin >> s;
    if (s == "NO") {
      v[i + k - 1] = v[i];
    }
  }
  for (int i = 0; i < n; i++) cout << v[i].first << endl;
  return 0;
}
