Secure Doors Solution:

#include <bits/stdc++.h>

using namespace std;

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

    int actions;
    cin >> actions;
    string action;
    string name;
    set<string> ppl_inside;
    bool inside = false;

    while(actions--){
        cin >> action;
        cin >> name;
        inside = ppl_inside.find(name) != ppl_inside.end();
        if(action == "entry"){
            cout << name << " entered";
            if(inside){
                cout << " (ANOMALY)";
            } else {
                ppl_inside.insert(name);
            }
            cout << endl;
        }
        else{
            cout << name << " exited";
            if(!inside){
                cout << " (ANOMALY)";
            } else {
                ppl_inside.erase(name);
            }
            cout << endl;
        }
    }
    
    return 0;
}