#include <iostream>
using namespace std;

int main()
{
	int n, m, nonMoved;
	cin >> n >> m;
	nonMoved = n;
	int accessRecord[n + 1] = {0};
	int temp;
	for (int i = 1; i <= m; i++) {
		cin >> temp;
		if (accessRecord[temp] == 0)
			nonMoved--;
		accessRecord[temp] = i;
	}

	int arrange[nonMoved + m + 1] = {0};
	for (int i = n, j = 1; i > 0; i--) {
		if (accessRecord[i] == 0)
			arrange[j++] = i;
		else
			arrange[nonMoved + accessRecord[i] + 1] = i;
	}

	for (int i = nonMoved + m + 1; i > 0; i--)
		if (arrange[i] != 0)
			cout << arrange[i] << endl;

	return 0;
}