 
int main()
{
		int k,i=0, n = 0;
		int count[26]={0};
		int pos [26]={0}; 
		scanf("%d",&n);
		char array[100001] ;
		for(i = 0 ; i<n ; i++)
		{
			for(k=0;k<26;k++){
				pos[k]=101;count[k] =0;
			}
			scanf("%s",&array);
			int j = 0;
			int flag = -1;
			for(;j<strlen(array);j++)
			{
				if(count[array[j]-'a']==0)pos[array[j]-'a']=j;
				count[array[j]-'a']++;
			}
			int min_pos = 100;
			int tpos=-1;
			for(j=0;j<26;j++){
				if(count[j]==1){
					if(min_pos>pos[j]){min_pos = pos[j];tpos = j;}
				}
			}
			if(min_pos == 100)printf("no\n");
			else printf("%c\n",tpos+'a');
		}
		
		return 0;
}