#include <bits/stdc++.h>

using namespace std;
const int MAXN = 100010;
int n, m, f1[MAXN], f2[MAXN], f[MAXN], used[MAXN];
int main() {
	int n,m; scanf("%d%d", &n, &m);
	for (int i = 0, a; i < m; i++) {
		scanf("%d", &a);
		used[f1[i] = a] = 1;
	}
	for (int i = 1, j = 0; i <= n; i++) if (!used[i]) f2[j++] = i;
	merge(f1,f1+m,f2,f2+(n-m),f);
	for(int i = 0; i < n; i++) printf("%d\n", f[i]);
	return 0;
}