#include <bits/stdc++.h>
using namespace std;
string s[100], ans[100];
int main() {
  int n, k;
  cin >> n >> k;
  int cnt = 0;
  string last;
  for (int i = 0; i < n - k + 1; i++) {
    cin >> s[i];
  }
  for (int i = 0; i < k - 1; i++) {
    ans[i] = "";
    ans[i] += (cnt / 26 + 'A');
    ans[i] += ((cnt % 26) + 'a');
    cnt++;
  }
  for (int i = k - 1; i < n; i++) {
    if (s[i - k + 1] == "YES") {
      ans[i] = "";
      ans[i] += (cnt / 26 + 'A');
      ans[i] += ((cnt % 26) + 'a');
      cnt++;
    } else {
      ans[i] = ans[i - k + 1];
    }
  }
  for (int i = 0; i < n; i++) cout << ans[i] << endl;
  return 0;
}
