int main()
{
	int t=0,i=0,j=0,k=0,time[26][2],min=0;
	char x=' ',str[100000];
	cin>>t;
	cin.get();
	for(i=0;i<26;i++)
	{time[i][0]=-1;time[i][1]=0;}//time[i][0]??????,time[i][1]????
	for(i=0;i<t;i++)
	{
		for(j=0;;j++)
		{
			x=getchar();
			//cout<<"x="<<x<<endl;//explain
			if(x=='\n')
			{
				min=999999;
				for(k=0;k<26;k++)
				{
					if(time[k][1]==1&&time[k][0]<min)
						min=time[k][0];
				}
				if(min==999999)
					cout<<"no"<<endl;
				else
				{
					cout<<str[min]<<endl;//cout
				}
				break;
			}
			else
			{
				str[j]=x;
				if(time[x-97][1]==0)
				{
					time[x-97][0]=j;
					time[x-97][1]++;
				}
				else
					time[x-97][1]++;
			}
		}
		for(k=0;k<26;k++)
		{
			//cout<<"time["<<k<<"][1]="<<time[k][1]<<endl;//???????
			time[k][0]=-1;
			time[k][1]=0;
		}
		//cout<<"i="<<i<<endl;//explain
	}
	return 0;
}