Example

Input

5 3
4
2
5


Output

5
2
4
1
3
#include<iostream>
#include<vector>
#define rep(i,n) for(int i=0;i<(int)(n);i++)
using namespace std;

int main(){
  int n,m;
  cin >> n >> m;
  vector<int> use(n+1,0),e(m);
  
  rep(i,m) cin >> e[i];
  
  rep(i,m){
    int v = e[m-1-i];
    if(!use[v]){
      cout << v << endl;
      use[v] = 1;
    }
  }

  rep(i,n){
    if(!use[i+1]) cout << i + 1 << endl;
  }
}
  