#include<iostream>
#include<string>

using namespace std;

#define ALPHA_MAX 26
int main(){

	int NM;
	string S;
	int Slen;
	int to[ALPHA_MAX];
	int from[ALPHA_MAX];

	for(int i=0;i<ALPHA_MAX;i++){
		to[i]=-1;
		from[i]=-1;
	}

	Slen=0;

	for(int i=0;i<2;i++){
		cin>>NM;
		for(int j=0;j<NM;j++){
			cin>>S;
			if(i==0) Slen+=S.size();
			for(int k=0;k<S.size()-1;k++){
				from[S[k+1]-'A']=S[k]-'A';
				to[S[k]-'A']=S[k+1]-'A';
			}
		}
	}

	string ans="";
	for(int i=0;i<ALPHA_MAX;i++){
		if(from[i]==-1&&to[i]!=-1){
			int j;
			for(j=i;to[j]!=-1;j=to[j]){
				ans+=j+'A';
			}
			ans+=j+'A';
			break;
		}
	}

	if(Slen==1) cout<<S<<endl;
	else if(ans.size()==Slen) cout<<ans<<endl;
	else cout<<"-1"<<endl;
}