Write a program that memorizes whether each of the \(N\) people were called out, while simulating the actions of person \(1\), person \(2\), \(\ldots\), and person \(N\) in this order, and your program will be accepted.

A sample code in C++ language follows.

#include <iostream>
using namespace std;

int n;
int a[200001];
bool b[200001];

int main(void)
{
  cin >> n;
  for(int i = 1; i <= n; i++) cin >> a[i];
  for(int i = 1; i <= n; i++) if(!b[i]) b[a[i]] = true;
  
  int k = 0;
  for(int i = 1; i <= n; i++) if(!b[i]) k++;
  cout << k << endl;
  for(int i = 1; i <= n; i++) if(!b[i]) cout << i << " ";
  cout << endl;
  
  return 0;
}