#include <bits/stdc++.h>

using namespace std;

#define forn(i, n) for (int i = 0; i < (int)(n); ++i)

struct randomSet {
	unordered_map<int> m;
	vector<int> v;
	void add(int x) {
		if (m.find(x) != m.end()) {
			return;
		}
		m[x] = v.size();
		v.push_back(x);
	}
	void del(int x) {
		if (m.find(x) == m.end()) {
			return;
		}
		int i = m[x];
		v[i] = v.back();
		v.pop_back();
		m[v[i]] = i;
	}
	int getRand() {
		return v[rand() % v.size()];
	}
};

int main() {

}