
struct String
{
	int number;
	int sequence;
	int flag;
}b[26],c[26];//???

int main()
{
	int t;
	int i,count=0,x;
	char string[100];
//	char *p;
//	p=string;
	int flag=1;
	scanf("%d\n",&t);
	while(count<t)
	{
		for(i=0;i<26;i++)
		{
			b[i].number=0;
			b[i].sequence=0;
			b[i].flag=1;
		}//??t????????
		for(i=0;i<26;i++)
		{
			c[i].number=0;
			c[i].sequence=0;
			c[i].flag=1;
		}//??t????????
		gets(string);
//		puts(string);
		i=0;
		while(string[i]!='\0')
		{
			x=string[i]-97;
			b[x].number++;
			if(b[x].flag==1)
			{	
				b[x].sequence=i;
				b[x].flag=0;
			}
			i++;
		}//??????????
		int j=0,min_number;
		for(i=0;i<26;i++)
		{
			if(b[i].number==1){
				flag=0;
				break;}
			else flag=1;
		}//???1??
		if(flag==0)//????
		{
			for(i=0,j=0;i<26;i++)
			{
				if(b[i].number==1)
				{
					c[j].number=i;
					c[j].sequence=b[i].sequence;
					j++;
				}//???c??
			}
			for(i=0;i<j;i++)
			{
				int min=c[0].sequence;
				min_number=c[0].number;
				if(c[i].sequence<min)
				{
					min=c[i].sequence;
					min_number=c[i].number;
				}
			}
			printf("%c\n",min_number+97);
		}else if(flag==1)//????????
		{
			printf("no\n");
		}
		count++;
	}
	return 0;
}