#include "bits/stdc++.h"
using namespace std;
#define rep(i,n) for(int (i)=0;(i)<(int)(n);++(i))
#define rer(i,l,u) for(int (i)=(int)(l);(i)<=(int)(u);++(i))
#define reu(i,l,u) for(int (i)=(int)(l);(i)<(int)(u);++(i))
static const int INF = 0x3f3f3f3f; static const long long INFL = 0x3f3f3f3f3f3f3f3fLL;
typedef vector<int> vi; typedef pair<int, int> pii; typedef vector<pair<int, int> > vpii; typedef long long ll;
template<typename T, typename U> static void amin(T &x, U y) { if (y < x) x = y; }
template<typename T, typename U> static void amax(T &x, U y) { if (x < y) x = y; }

int main() {
	int N;
	{
		vector<int> next(26, -1);
		vector<string> words;
		vector<bool> head(26);
		rep(k, 2) {
			int N;
			scanf("%d", &N);
			rep(i, N) {
				char buf[101];
				scanf("%s", buf);
				head[*buf - 'A'] = true;
				words.push_back(buf);
				for (const char *p = buf; *p; ++ p)
					if (p[1])
						next[p[0] - 'A'] = p[1] - 'A';
			}
		}
		rep(a, 26) if (next[a] != -1)
			head[next[a]] = false;
		int a = (int)(find(head.begin(), head.end(), true) - head.begin());
		string ans;
		if (a != 26) {
			while (a != -1) {
				if (count(ans.begin(), ans.end(), 'A' + a)) break;
				ans += char('A' + a);
				a = next[a];
			}
		}
		bool ok = true;
		for (string word : words)
			ok &= ans.find(word) != string::npos;
		if (!ok) {
			puts("-1");
		} else {
			puts(ans.c_str());
		}
	}
	return 0;
}