#include <bits/stdc++.h>
using namespace std;
const int INF = 1e9 + 7;
using namespace std;
const string tp[4] = {"aaaa", "aabb", "abab", "abba"};
int n, k;
int m;
string w[10000];
int prime(int x) {
  if (x == 1) return 0;
  for (int i = 2; i * i <= x; i++)
    if (x % i == 0) return 0;
  return 1;
}
int check(int x, int y) {
  if (x > n || x < 1 || y >= m || y < 0) return 0;
  return 1;
}
long long gcd(long long a, long long b) {
  if (b == 0) {
    return a;
  }
  return gcd(b, a % b);
}
int vowel(char t) {
  if (t == 'a' || t == 'e' || t == 'i' || t == 'o' || t == 'u') return 1;
  return 0;
}
int main() {
  cin >> n >> k;
  int bad = 0;
  for (int i = 0; i < n * 4; i++) {
    string s;
    cin >> s;
    w[i] = "";
    int l = 0;
    while (l < k and s.size()) {
      char c = s[s.size() - 1];
      w[i] += c;
      s.erase(s.size() - 1);
      l += vowel(c);
    }
    if (l < k) {
      bad = 1;
    }
  }
  if (!bad) {
    for (int t = 0; t < 4; t++) {
      int ok2 = 1;
      for (int i = 0; i < n * 4; i += 4) {
        int ok = 1;
        for (int p = 0; p < 4 and ok; p++) {
          for (int q = p + 1; q < 4 and ok; q++) {
            if (tp[t][p] == tp[t][q] and w[i + p] != w[i + q]) {
              ok = 0;
            }
          }
        }
        if (!ok) {
          ok2 = 0;
          break;
        }
      }
      if (ok2) {
        cout << tp[t];
        return 0;
      }
    }
  }
  cout << "NO";
  return 0;
}
