#include <set>
#include <unordered_set>
#include <iostream>

using namespace std;

int main() {
    int n;
    string word;
    cin >> n;
    set<string> words;
    unordered_set<string> res;
    for (int i = 0; i < n; i++)
    {
        cin >> word;
        if (words.find(word) == words.end())
            words.insert(word);
        else
            res.insert(word);
    }
    if (res.size() != 0)
        for (auto i : res)
            cout << i << endl;
    else
        cout << "Understandable, have a great day" << endl;
    return 0;
}