#include <algorithm>
#include <vector>
#include <cfloat>
#include <string>
#include <cmath>
#include <set>
#include <cstdlib>
#include <map>
#include <ctime>
#include <iomanip>
#include <functional>
#include <deque>
#include <iostream>
#include <cstring>
#include <queue>
#include <cstdio>
#include <stack>
#include <climits>
#include <sys/time.h>
#include <cctype>

using namespace std;

typedef long long ll;

int main() {
  int n;
  scanf("%d", &n);

  int memo[12] = {50965598, 138640614, 86894790, 22969011, 137866584, 12805388, 102696496, 169269628, 196679944, 213985204, 79308356};

  set <int> hash;
  for (int i = 0; i < n; i++) {
    char s[12];
    scanf("%s", s);
    int t = 0;
    for (int j = 0; j < 12; j++) {
      t += s[j]*memo[j];
    }
    hash.insert(t);
  }
  if (hash.size() >= 129599) {
    puts("NO");
    return 0;
  }

  int ind1[6], ind2[6];
  for (int i = 0; i < 6; i++) {
    ind1[i] = i;
    ind2[i] = i;
  }

  char str[12] = "inabameguru";
  do {
    do {
      char ans[12];
      int temp = 0;
      for (int i = 0; i < 6; i++) {
	temp += str[2*ind1[i]]*memo[2*i];
	ans[2*i] = str[2*ind1[i]];
      }
      for (int i = 0; i < 5; i++) {
	temp += str[2*ind2[i]+1]*memo[2*i+1];
	ans[2*i+1] = str[2*ind2[i]+1];
      }
      ans[11] = '\0';

      if (hash.find(temp) == hash.end()) {
      	puts(ans);
      	return 0;
      }
      for (int i = 0; i < 10; i++) {
	temp += ans[i]*memo[i+1]-ans[i]*memo[i];
	temp += ans[i+1]*memo[i]-ans[i+1]*memo[i+1];
	swap(ans[i], ans[i+1]);
	if (hash.find(temp) == hash.end()) {
	  puts(ans);
	  return 0;
	}
      }

    } while(next_permutation(ind2, ind2+5));
  } while(next_permutation(ind1, ind1+6));
}