#include <bits/stdc++.h>
#define rep(i,n)for(int i=0;i<(n);i++)
using namespace std;

vector<int>E[26];
int in[26];
bool used[26];

int main(){
	rep(i,2){
		int n;scanf("%d",&n);
		rep(k,n){
			string s;cin>>s;
			rep(j,s.size()-1){
				E[s[j]-'A'].push_back(s[j+1]-'A');
				in[s[j+1]-'A']++;
				used[s[j]-'A']=true;
			}
			used[s.back()-'A']=true;
		}
	}
	queue<int>que;
	rep(i,26){
		if(used[i]&&in[i]==0)que.push(i);
	}
	string ans;
	while(!que.empty()){
		if(que.size()>1){puts("-1");return 0;}
		int p=que.front();que.pop();
		ans+=p+'A';
		for(auto u:E[p]){
			in[u]--;
			if(!in[u])que.push(u);
		}
	}
	cout<<ans<<endl;
}