#include <iostream>
using namespace std;
int main()
{
    int N, M;
    int a[1000];
    int b[1000];
    int i, j, sum = 0;
    cin >> N >> M;
    for (i = 0 ; i < M ; i++){
        cin >> a[i];
    }
    for (i = 0 ; i < M ; i++){
        for (j = 0 ; j < N ; j++){
            if (a[i] == j && b[i] != -1){
                b[i] = -1;
                sum++;
            }
        }
        if (sum == N){
            cout << N << endl;
        }else{
            for (j = 0 ; j < N ; j++){
                if (a[j] != j){
                    cout << j << ' ';
                }
            }
            break;
        }
    }
    cout << endl;
}

哪里错了啊啊啊