#include <bits/stdc++.h>

using namespace std;

int main() {
    freopen("bac1.in", "r", stdin);

    int n;
    cin >> n;

    int last = 1;
    bool ok = false;
    int x;
    while (cin >> x) {
        for (int j = last; j < x; j ++) {
            ok = true;
            cout << j << " ";
        }
        last = x + 1;
    }
    for (int i = last; i <= n; i++) {
        cout << i << " ";
        ok = true;
    }

    if (!ok) {
        cout << "nu exista\n";
    }

    return 0;
}