#include <bits/stdc++.h>
using namespace std;
int a[1005];
int main() {
	int n, m;
	cin >> n >> m;
	int num, k = 0;
	for (int i = 1; i <= m; i++) {
		cin >> num;
		a[num]++;
	}
	for (int i = 1; i < n; i++) {
		if (a[i] == 0) {
			cout << i << " ";
			k++;
		}
	}
	if (k == 0) cout << n << endl;
	return 0;
}

样例过，但WA。。。 dalao求教