#include <bits/stdc++.h>
#define ll long long
#define M 1000000007
using namespace std;
ll n,m,cnt,c,a[214514],t[214514];
bool b[114514];
int main(){
	ios_base::sync_with_stdio(false);
//	freopen("ex_A2.in","r",stdin);
//	freopen("ex_A2.out","w",stdout);
	cin>>n>>m;
	for(int i=1;i<=m;i++){
		cin>>a[i];
		b[a[i]]=true;
		t[i]=i+1;
	}
	t[0]=1;
	a[m+1]=114514;
	t[m+1]=-1;
	c=m+2;
	for(int i=1;i<=n;i++){
		if(b[i]) continue;
		while(!(i>a[cnt]&&i<a[t[cnt]])){
			cnt=t[cnt];
		}
		t[c]=t[cnt];
		t[cnt]=c;
		a[c]=i;
		c++;
	}
	cnt=t[0];
	while(cnt!=-1&&cnt!=m+1){
		cout<<a[cnt]<<" ";
		cnt=t[cnt];
	}
	
	return 0;
}