import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;
import java.util.NoSuchElementException;

public class Main {
	public static void main(String[] args) throws FileNotFoundException {
		long t = System.currentTimeMillis();
		new Main().run();
		System.err.println(System.currentTimeMillis() - t);
	}
	
	void run() {
		FastScanner sc = new FastScanner();
		int N=sc.nextInt();
		String[] A=new String[N];
		for(int i=0;i<N;++i)A[i]=sc.next();
		int M=sc.nextInt();
		String[] B=new String[M];
		for(int i=0;i<M;++i)B[i]=sc.next();
		String[] AB=new String[N+M];
		for(int i=0;i<N;++i)AB[i]=A[i];
		for(int i=0;i<M;++i)AB[i+N]=B[i];
		boolean[] used=new boolean[N+M];
		boolean update=true;
		out:while(update){
			update=false;
			for(int p=0;p<AB.length;++p) {
				if(used[p])continue;
				for(int q=0;q<AB.length;++q) {
					if(used[q]||p==q)continue;
					//AB[q]が先
					for(int j=0;j<AB[q].length();++j) {
						if(AB[q].length()-j>AB[p].length())continue;
						if(AB[p].substring(0, AB[q].length()-j).equals(AB[q].substring(j,AB[q].length()))) {
							update=true;
							used[q]=true;
							AB[p]=AB[q].substring(0,j)+AB[p];
							continue out;
						}
					}
					//AB[q]がAB[p]に完全に含まれる。
					for(int j=0;j<=AB[p].length()-AB[q].length();++j) {
						if(AB[q].equals(AB[p].substring(j,j+AB[q].length()))) {
							update=true;
							used[q]=true;
							continue out;
						}
					}
				}
			}
		}
		int cnt=0;
		String ans="";
		for(int i=0;i<AB.length;++i) {
			if(!used[i]) {
				++cnt;ans=AB[i];
			}
		}
		System.out.println(cnt!=1?-1:ans);
	}

	
	
	static 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;}
    private void skipUnprintable() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;}
    public boolean hasNext() { skipUnprintable(); 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() {
    	return (int)nextLong();
    }
}