#include <bits/stdc++.h>
using namespace std;
string s[55];
int n, k, dem, ok;
string luu[55];
void duyet(int leng, int u, string str) {
  if (u == leng) {
    luu[++dem] = str;
    if (dem == n) ok = 1;
    return;
  }
  if (u == 0) {
    for (char c = 'A'; c <= 'Z'; ++c) {
      str += c;
      duyet(leng, u + 1, str);
      if (ok) return;
      str = "";
    }
  } else {
    for (char c = 'a'; c <= 'z'; ++c) {
      str += c;
      duyet(leng, u + 1, str);
      if (ok) return;
      int xx = str.size();
      str.erase(xx - 1, 1);
    }
  }
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> n >> k;
  for (int i = (1); i <= (n - k + 1); ++i) cin >> s[i];
  for (int i = (1); i <= (10); ++i) {
    duyet(i, 0, "");
    if (ok) break;
  }
  for (int i = (1); i <= (n - k + 1); ++i) {
    if (s[i] == "NO") {
      luu[i + k - 1] = luu[i];
    }
  }
  for (int i = (1); i <= (n); ++i) cout << luu[i] << ' ';
  return 0;
}
