import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.HashSet;
import java.util.NoSuchElementException;

class Main {
	public static void main(String[] args) {
		new Main().run();
	}
	
	boolean isVowel(char c) {
		return c=='a'||c=='i'||c=='u'||c=='e'||c=='o';
	}
	
	boolean check(int[] ord) {
		int p=0;
		while(p<ord.length) {
			if(isVowel(a[ord[p]])){
				p+=1;
			}else if(p+1<ord.length&&isVowel(a[ord[p+1]])) {
				p+=2;
			}else {
				return false;
			}
		}
		return true;
	}
	
	char[] a= {'a','u','i','n','b','m','e','g','r'};
	
	String toString(int[] ord) {
		StringBuilder cur=new StringBuilder();
		for(int i=0;i<ord.length;++i) {
			cur=cur.append(a[ord[i]]);
		}
		return cur.toString();
	}
	
	void run() {
		FastScanner sc=new FastScanner();
		int N=sc.nextInt();
		HashSet<String> set=new HashSet<>();
		for(int i=0;i<N;++i)set.add(sc.next());
		int[] ord = {0,0,1,1,2,3,4,5,6,7,8};
		do {
			if(check(ord)&&!set.contains(toString(ord))) {
				System.out.println(toString(ord));
				return;
			}
		}while(nextPermutation(ord));
		System.out.println("NO");
	}
	
	boolean nextPermutation(int[] a) {
		int p=a.length-1;
		while(p-1>=0&&a[p-1]>=a[p])--p;
		if(p==0)return false;
		int q=p;
		while(q+1<a.length&&a[q+1]>a[p-1])++q;
		a[q]^=a[p-1];a[p-1]^=a[q];a[q]^=a[p-1];
		int s=p,t=a.length-1;
		while(s<t) {
			a[s]^=a[t];a[t]^=a[s];a[s]^=a[t];
			++s;--t;
		}
		return true;
	}
	
	void tr(Object...objects) {System.out.println(Arrays.deepToString(objects));}
}


class FastScanner {
    private final InputStream in = System.in;
    private final byte[] buffer = new byte[1024];
    private int ptr = 0;
    private int buflen = 0;
    private boolean hasNextByte() {
        if (ptr < buflen) {
            return true;
        }else{
            ptr = 0;
            try {
                buflen = in.read(buffer);
            } catch (IOException e) {
                e.printStackTrace();
            }
            if (buflen <= 0) {
                return false;
            }
        }
        return true;
    }
    private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
    private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
    public boolean hasNext() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++; return hasNextByte();}
    public String next() {
        if (!hasNext()) throw new NoSuchElementException();
        StringBuilder sb = new StringBuilder();
        int b = readByte();
        while(isPrintableChar(b)) {
            sb.appendCodePoint(b);
            b = readByte();
        }
        return sb.toString();
    }
    public long nextLong() {
        if (!hasNext()) throw new NoSuchElementException();
        long n = 0;
        boolean minus = false;
        int b = readByte();
        if (b == '-') {
            minus = true;
            b = readByte();
        }
        if (b < '0' || '9' < b) {
            throw new NumberFormatException();
        }
        while(true){
            if ('0' <= b && b <= '9') {
                n *= 10;
                n += b - '0';
            }else if(b == -1 || !isPrintableChar(b)){
                return minus ? -n : n;
            }else{
                throw new NumberFormatException();
            }
            b = readByte();
        }
    }
    public int nextInt() {
        long nl = nextLong();
        if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE) throw new NumberFormatException();
        return (int) nl;
    }
    public double nextDouble() { return Double.parseDouble(next());}
}