#include <bits/stdc++.h>
using namespace std;
 
int main() {
    int N;
    cin >> N;
    vector<int> zapatillas(N);
    unordered_map<int, int> conteo;
 
    for (int i = 0; i < N; i++) {
        cin >> zapatillas[i];
        conteo[zapatillas[i]]++;
    }
 
    vector<int> a_tirar;
    int total_a_tirar = 0;
 
    for (const auto& par : conteo) {
        if (par.second % 2 != 0) {
            a_tirar.push_back(par.first);
            total_a_tirar += 1;
        }
    }
 
    if (total_a_tirar == 0) {
        cout << ":D" << endl;
    } else {
        for (int id : a_tirar) {
            cout << id << " ";
        }
        cout << endl;
    }
 
    cout << total_a_tirar << endl;
    cout << N - total_a_tirar << endl;
 
    return 0;
}

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