Saving Princess Peach Solution:

#include <bits/stdc++.h>
using namespace std;


int main(){
    // #ifndef TESTING
    // freopen("input.txt", "r", stdin);
    // freopen("output.txt", "w", stdout);
    // #endif

    int nObstacles, nFound;
    cin >> nObstacles >> nFound;
    set<int> found;
    while(nFound--){
        int obstacle;
        cin >> obstacle;
        found.insert(obstacle);
    }
    for(int i = 0; i < nObstacles; i++){
        auto it = found.find(i);
        if(it == found.end()){
            cout << i << endl;
        }
    }
    cout << "Mario got " << found.size() << " of the dangerous obstacles." << endl;

    return 0;   
}