#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>
using namespace std;
const int maxnode = 2396744;
typedef pair<int,int> pii;
//const int maxnode = 1000000;
const int sigma_size = 8;

struct Trie{
    int ch[maxnode][sigma_size];
    int fa[maxnode];
    char let[maxnode];
    int sz;
    void init()
    {
        sz=1;
        memset(ch[0],0,sizeof(ch[0]));
    }
    int idx(char c) {return c-‘A‘;}
    void insert(char *s,int n)
    {
        int u=0;
        for(int i=0;i<n;++i)
        {
            int c=idx(s[i]);
            if(!ch[u][c])
            {
                memset(ch[sz],0,sizeof(ch[sz]));
                fa[sz]=u;
                let[sz]=c+‘A‘;
                ch[u][c]=sz++;
                if(sz>=maxnode)
                    cout<<"fuck this memory"<<endl;
            }
            u=ch[u][c];
        }
    }
    char ans[10];
    int ansz;
    void bfs()
    {
        int u;
        queue<int> q;
        q.push(0);
        while(!q.empty())
        {
            u=q.front();
            q.pop();
            for(int i=0;i<sigma_size;++i)
            {
                if(ch[u][i])
                {
                    q.push(ch[u][i]);
                }
                else
                {//find
//                    cout<<"find "<<u<<endl;
                    ans[0]=i+‘A‘;
                    ansz=1;
                    print(u);
                    return;
                }
            }
        }
    }
    void print(int u)
    {
        while(u)
        {
//            cout<<".";
            ans[ansz++]=let[u];
            u=fa[u];
        }
//        cout<<"sz="<<ansz<<endl;
        for(int i=ansz-1;i>=0;--i)
            printf("%c",ans[i]);
        printf("\n");
    }
    void text()
    {
        int i;
        for(i=0;i<sz;++i)
        {
            printf("%d: fa=%d let=%c\n",i,fa[i],let[i]);
        }
    }
};

char ms[1000005];
Trie tree;

void run()
{
    int i,len;
    scanf("%s",ms);
    len = strlen(ms);
    tree.init();
    for(i=0;i<len;++i)
    {
        tree.insert(ms+i,min(8,len-i));
    }
//    tree.text();
    tree.bfs();
}

int main()
{
    //freopen("in","r",stdin);
    int _;
    scanf("%d",&_);
    while(_--)
        run();
    return 0;
}