//bzoj 1195
#include<iostream>
#include<cstring>
#include<cstdio>
#include<queue>
#define ll long long
#define mp make_pair
#define M(a) memset(a,0,sizeof a)
#define fo(i,j,k) for(i=j;i<=k;i++)
using namespace std;
const int mxn=605;
char s[mxn];
int n,m,num,top;
bool vis[mxn][1<<12];
int pre[mxn][1<<12][2],self[mxn],st[mxn];
queue <int> Q;
queue < pair<int,int> > q;
struct node {int cnt,fail,son[30];} a[mxn];
inline void trie(int w)
{
scanf("%s",s+1);
int i,j,x=0,len=strlen(s+1);
fo(i,1,len)
{
int c=s[i]-'A'+1;
if(!a[x].son[c])
a[x].son[c]=(++num);
x=a[x].son[c];
}
a[x].cnt|=(1<<w-1);
}
inline void build()
{
int i,j,T=0;
fo(i,1,26) if(a[0].son[i]) Q.push(a[0].son[i]);
while(!Q.empty())
{
int x=Q.front();Q.pop();
int fail=a[x].fail;
fo(i,1,26)
{
int y=a[x].son[i];
if(y) Q.push(y),a[y].fail=a[fail].son[i];
else a[x].son[i]=a[fail].son[i];
}
a[x].cnt|=a[fail].cnt;
}
}
inline void print(int x,int step)
{
st[++top]=self[x];
while(pre[x][step][0])
{
int y=pre[x][step][0],now=pre[x][step][1];
x=y,step=now;
st[++top]=self[x];
}
for(int i=top;i;i--) if(st[i]) printf("%c",st[i]+'A'-1);
}
inline void bfs()
{
int i,end=(1<<n)-1;
q.push(mp(0,0)),vis[0][0]=1;
while(!q.empty())
{
int x=q.front().first,now=q.front().second;
q.pop();
fo(i,1,26)
{
int y=a[x].son[i];
int tmp=now|a[y].cnt;
if(!vis[y][tmp])
{
q.push(mp(y,tmp)),vis[y][tmp]=1;
pre[y][tmp][0]=x,pre[y][tmp][1]=now,self[y]=i;
if(tmp==end)
{
print(y,tmp);
return;
}
}
}
}
}
int main()
{
int i,j;
scanf("%d",&n);
fo(i,1,n) trie(i);
build();
// printf("num=%d\n",num);
bfs();
return 0;
}
/*
6
AAA
AAB
AAC
AAD
AAE
AAF
*/
