TRIE

//TRIE Data Structure: Check if prefix exist.
#include <bits/stdc++.h>
using namespace std;
#define Size 150005

class Trie {
    bool found;
    Trie *child[10];

public:
    Trie() {
        found = false;
        for (int i = 0; i < 10; i++)
            child[i] = NULL;
    }
    void delete_trie() {
        for (int i = 0; i < 10; i++)
            if (child[i] != NULL) {
                child[i]->delete_trie();
                delete child[i];
            }
    }
    bool insert_word(string &word, int pos) {
        if (found){
            return false;
        }
        if (pos == (int)word.length()){
            return found = true;
        }
        int c = (int)(word[pos] - '0');
        if (child[c] == NULL) {
            child[c] = new Trie();
        }
        return child[c]->insert_word(word, ++pos);
    }
}*root;

int N;
string numbers[10005];

bool cmp(string a,string b){
    if(a.length()<b.length()) return true;
    if(a.length()>b.length()) return false;
    if(a < b) return true;
    return false;
}

int main() {
    int nCase;
    cin >> nCase;
    for (int cs = 1; cs <= nCase; cs++) {
        cin >> N;
        root = new Trie();
        for (int i = 0; i < N; i++) {
            cin >> numbers[i];
        }
        sort(numbers,numbers+N,cmp);
        bool f = true;
        for (int i = 0; i < N; i++) {
            f = root->insert_word(numbers[i],0);
            if(f == false) break;
        }
        if (f == true) {
            printf("Case %d: YES\n",cs);
        } else {
            printf("Case %d: NO\n",cs);
        }
        root->delete_trie();
        delete root;
    }
    return 0;
}