#define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES

#include <bits/stdc++.h>
using namespace std;
using i32 = int; using i64 = long long int; using f64 = double; using str = string;
template <typename T> using vec = vector<T>;
template <typename T> using heap = priority_queue<T>;
void in() {}; template <typename T, typename...TS> void in(T &&x, TS &&...xs) { cin >> x; in(move(xs)...); };
template <typename T> void _out(char *sep, char *end, T &&x) { cout << x << end; };
template <typename T, typename...TS> void _out(char *sep, char *end, T &&x, TS &&...xs) { cout << x << sep; _out(sep, end, move(xs)...); }
#define indef(t, ...) t __VA_ARGS__; in(__VA_ARGS__)
#define get(t) []{ t _; cin >> _; return _; }()
#define put(...) _out("", "", __VA_ARGS__)
#define out(...) _out(" ", "\n", __VA_ARGS__)
#define times(n, i) for (i32 i =  0 ; i <  (n); ++i)
#define range(a, b, i) for (i32 i = (a); i <  (b); ++i)
#define upto(a, b, i) for (i32 i = (a); i <= (b); ++i)
#define downto(a, b, i) for (i32 i = (a); i >= (b); --i)
#define all(xs) (xs).begin(), (xs).end()
#define sortall(xs) sort(all(xs))
#define reverseall(xs) reverse(all(xs))
#define even(x) (((x) & 1) == 0)
#define odd(x) (((x) & 1) == 1)
#define append emplace_back
#define findge lower_bound
#define findgt upper_bound
const i64 MOD = 1000000007;
const f64 EPS = 1e-10;

i32 l[26], r[26];
bool q[26];

i32 main()
{
	memset(l, -1, sizeof(l));
	memset(r, -1, sizeof(r));
	indef(i32, n);
	times(n, _) {
		indef(str, a);
		range(1, a.size(), i) {
			l[a[i] - 'A'] = a[i - 1] - 'A';
		}
		range(0, a.size() - 1, i) {
			r[a[i] - 'A'] = a[i + 1] - 'A';
		}
		for (char c : a) {
			q[c - 'A'] = true;
		}
	}
	indef(i32, m);
	times(m, _) {
		indef(str, b);
		range(1, b.size(), i) {
			l[b[i] - 'A'] = b[i - 1] - 'A';
		}
		range(0, b.size() - 1, i) {
			r[b[i] - 'A'] = b[i + 1] - 'A';
		}
		for (char c : b) {
			q[c - 'A'] = true;
		}
	}
	str ans = "";
	times(26, i) {
		if (r[i] == -1) continue;

		i32 t = i;
		while (l[t] > -1) {
			t = l[t];
		}

		while (r[t] > -1) {
			ans += 'A' + t;
			t = r[t];
		}
		ans += 'A' + t;
		break;
	}
	i32 cnt = 0;
	times(26, i) {
		cnt += q[i] ? 1 : 0;
	}
	if (cnt == 1) {
		ans = "";
		times(26, i) {
			if (q[i]) {
				ans += 'A' + i;
			}
		}
	}

	bool w[26] = {};
	for (char c : ans) {
		w[c - 'A'] = true;
	}
	times(26, i) {
		if (w[i] != q[i]) {
			out(-1);
			return 0;
		}
	}
	
	out(ans);
	return 0;

}