int use[26];
char s[1000010];
int main(){
    int n,i,j;
    scanf("%d",&n);
    for(j=0;j<n;j++){
        for(i=0;i<26;i++)
            use[i]=-1;
        scanf("%s",s);
        int l=strlen(s);
        for(i=0;i<l;i++){
            if(use[s[i]-'a']>=0)
                use[s[i]-'a']=-2;
            if(use[s[i]-'a']==-1)
                use[s[i]-'a']=i;
        }
        int minnum=10000000;char minn=-1;
        for(i=0;i<26;i++)
            if(use[i]>=0&&use[i]<minnum)
                minnum=use[i],minn=i+'a';
        if(minn==-1)printf("no\n");
        else printf("%c\n",minn);
    }
    return 0;
}
