#include "iostream"
using namespace std;
#define size 101
int father[size];
char ans[27];
int find(int k)
{
    return father[k]==k?k:father[k]=find(father[k]);
}
int main()
{
    int T, N, flag;
    char left, mid, right;
    cin>>T;
    while(T--)
    {
        cin>>N;
        for(int i=0; i<27; i++) 
            father[i]=i;
        flag = 0;
        for(int i=0; i<N; i++)
        {
            cin>>left>>mid>>right;
            if(left=='a' && right=='a') flag = 1;
            father[left-'a']=find(right-'a');
        }
        int j=0;
        for(int i=0; i<27; i++)
            if(father[i]==0) ans[j++]=i+'a';
        if(j==1 && flag) cout<<"a"<<endl;
        else if(j>1) 
        {
            for(int i=0; i<j-1; i++)
                cout<<ans[i]<<" ";
            cout<<ans[j-1]<<endl;
        }
        else cout<<"none"<<endl;
    }
}