int ith, start, len;

bool operator<(const struct entry &it) const{

if(len<it.len)return -1;

for(int i=0; i<len; i++){

if(strs[ith][i+start] < strs[it.ith][i+it.start]){

return -1;

}else if(strs[ith][i+start] > strs[it.ith][i+it.start]){

return 1;

}else{

continue;

}

}

return 0;

}

bool operator==(const struct entry &it) const{

if(len!=it.len)return false;

for(int i=0; i<len; i++){

if( strs[ith][i+start] == strs[it.ith][i+it.start]){

continue;

}else{

return false;

}

}

return true;

}

for(int i=mystr.start; i<mystr.start+mystr.len; i++){

cout<<strs[mystr.ith][i];

}cout<<endl;

unsigned int hash = 0;

for(int i=str.start; i<str.start+str.len; i++){

hash = (hash * seed + strs[str.ith][i])%MOD;

}

return hash%MOD;

int t_size = hash_table[h].size();

//cout<<"Inserting ";print(str);cout<<endl;

if(t_size==0){

pei ns(str, 1);

hash_table[h].push_back(ns);

}else{

bool exist = false;

for(int j=0; j<t_size; j++){

if(str == hash_table[h][j].first){

hash_table[h][j].second+=1;

//cout<<"current counting = "<<hash_table[h][j].second<<endl;

if(hash_table[h][j].second>half){

//answers.push_back( hash_table[h][j].first);

answers.insert(hash_table[h][j].first);

}

exist = true;

break;

}

}

if(!exist){

pei ns(str, 1);

hash_table[h].push_back(ns);

}

}

for(int i=0; i<MOD; i++)hash_table[i].clear();

unsigned RM = 1;

for(int i=1; i<cur_length; i++){

RM = (seed*RM)%MOD;

}

//cout<<"RM = "<<RM<<endl;

for(int i=0; i<N; i++){

int len = lens[i];

et net;

if(len<cur_length)continue;

net.ith = i;net.start=0;net.len=cur_length;

memset(mark,0,sizeof(mark));

myset.clear();

myset.insert(net);

for(int j=1; j+cur_length-1<len; j++){

net.ith = i;net.start=j;net.len=cur_length;

myset.insert(net);

}

//cout<<"set size = "<<myset.size()<<endl;

//cout<<"initial string is ";print(net);

//cout<<" with hash value "<<h<<endl;

set< et >::iterator myIt;

vector<int> tmp;

for(myIt = myset.begin(); myIt!=myset.end(); myIt++){

tmp.push_back(myIt->start);

mark[myIt->start] = 1;

}

net.ith = i;net.start=0;net.len=cur_length;

unsigned int h = hash_func(net);

insert(net, h);

for(int j=1; j+cur_length-1<len; j++){

unsigned int new_h = (h + MOD - (RM*strs[i][j-1])%MOD)%MOD ;

//cout<<"deleting "<<strs[i][j-1]<<" adding "<<strs[i][j+cur_length-1]<<endl;

new_h = (new_h*seed + strs[i][j+cur_length-1])%MOD;

net.ith = i;net.start=j;net.len=cur_length;

/*

h = new_h;

if(mark[j]){

insert(net, new_h);

}

}

}

if(answers.size()>0){

return true;

}

return false;

int max_length = -INF;

for(int i=0; i<N; i++){

lens[i] = strs[i].size();

max_length = max(max_length, lens[i]);

}

int low = 1, high = max_length, ans = -INF;

while(low<=high){

int mid = (high+low)/2;

if(judge(mid)){

ans = mid;

low = mid+1;

answer_buf = answers;

answers.clear();

}else{

high = mid-1;

}

}

if(answer_buf.size()==0){

cout<<"?"<<endl;

}else{

set<et>::iterator myIt;

vector< et > result;

for(myIt = answer_buf.begin(); myIt!=answer_buf.end(); myIt++){

//print( (*myIt) );

result.push_back( *myIt);

}

sort(result.begin(), result.end());

for(int i=0; i<result.size(); i++){

print(result[i]);

}

cout<<endl;

}

answers.clear();

answer_buf.clear();

while(cin>>N){

if(N==0)break;

for(int i=0; i<N; i++){

cin>>strs[i];

}

half=N/2;

work();

}

return 0;