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#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main() {
    int n;
    cin >> n;
    vector<int> numbers(2 * n);
    for (int &i : numbers) {
        cin >> i;
    }

    sort(numbers.begin(), numbers.end());

    vector<int> result(n);

    int prev = -2;
    int a = 0;
    for (int i : numbers) {
        if (abs(prev - i) > 1) {
            result[a] = i;
            a++;
            prev = i;
        }
    }

    if (a >= n && n != 1) {
        for (int i = 0; i < n; i++) {
            cout << result[i] << endl;
        }
    } else {
        cout << "impossible" << endl;
    }

    return 0;
}

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