#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, m;
  cin >> n >> m;
  string a;
  vector<string> v, b;
  bool u = false, l = false;
  for (int i = 0; i < 4 * n; i++) {
    cin >> a;
    int k = 0;
    u = false;
    for (int j = (int)a.length() - 1; j >= 0; j--) {
      if (a[j] == 'a' || a[j] == 'e' || a[j] == 'i' || a[j] == 'o' ||
          a[j] == 'u')
        k++;
      if (k >= m) {
        v.push_back(a.substr(j));
        u = true;
        break;
      }
    }
    if (!u) {
      l = true;
    }
  }
  if (l) {
    cout << "NO";
    return 0;
  }
  for (int i = 0; i < n; i++) {
    if (v[i * 4] == v[i * 4 + 1] && v[i * 4 + 1] == v[i * 4 + 2] &&
        v[i * 4 + 2] == v[i * 4 + 3]) {
      continue;
    }
    if (v[i * 4] == v[i * 4 + 1] && v[i * 4 + 2] == v[i * 4 + 3]) {
      b.push_back("aabb");
      continue;
    }
    if (v[i * 4 + 0] == v[i * 4 + 3] && v[i * 4 + 1] == v[i * 4 + 2]) {
      b.push_back("abba");
      continue;
    }
    if (v[i * 4 + 0] == v[i * 4 + 2] && v[i * 4 + 1] == v[i * 4 + 3]) {
      b.push_back("abab");
      continue;
    }
    cout << "NO";
    return 0;
  }
  if ((int)b.size() == 0) {
    cout << "aaaa";
    return 0;
  }
  bool h = true;
  for (int i = 1; i < (int)b.size(); i++) {
    if (b[i] != b[i - 1]) {
      h = false;
      break;
    }
  }
  if (h)
    cout << b[0];
  else
    cout << "NO";
  return 0;
}
