hdu 2328 Corporate Identity(kmp)

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
#include<string>
#include<vector>
#include<stack>
#include<bitset>
#include<cstdlib>
#include<cmath>
#include<set>
#include<list>
#include<deque>
#include<map>
#include<queue>
#define ll long long int
using namespace std;
inline ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
inline ll lcm(ll a,ll b){return a/gcd(a,b)*b;}
int moth[13]={0,31,28,31,30,31,30,31,31,30,31,30,31};
int dir[4][2]={1,0 ,0,1 ,-1,0 ,0,-1};
int dirs[8][2]={1,0 ,0,1 ,-1,0 ,0,-1, -1,-1 ,-1,1 ,1,-1 ,1,1};
const int inf=0x3f3f3f3f;
const ll mod=1e9+7;
int n;
string s[4007];
int nextt[500];
void getnext(string s){
    nextt[1]=0;
    int len=s.length();
    for(int i=2,j=0;i<=len;i++){
        while(j>0&&s[i-1]!=s[j]) j=nextt[j];
        if(s[i-1]==s[j]) j++;
        nextt[i]=j;
    }
}
bool kmp(string t,string p){
    int len1=p.length();
    int len2=t.length();
    for(int i=1,j=0;i<=len1;i++){
        while(j>0&&p[i-1]!=t[j]) j=nextt[j];
        if(p[i-1]==t[j]) j++;
        if(j==len2) return true;
    }
    return false;
}
int main(){
    ios::sync_with_stdio(false);
    while(cin>>n&&n){
        for(int i=0;i<n;i++)
            cin>>s[i];
        int len=s[0].length();
        string ans="";
        for(int i=len;i>=1;i--){
            for(int j=0;j<=len-i;j++){
                string temp=s[0].substr(j,i);
                getnext(temp);
                bool f=1;
                for(int k=0;k<n;k++)
                    if(!kmp(temp,s[k])){
                        f=0;
                        break;   //碰到假就弹出 
                    }
                if(f){
                    if(ans.size()<temp.size()) ans=temp;
                    else if(ans.size()==temp.size()) ans=min(ans,temp);
                }
            }
        }
        if(ans.size()<1) cout<<"IDENTITY LOST"<<endl;
        else cout<<ans<<endl;
            
    }
    return 0;
}