multiset写的有点答辩）

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

int read() {
    int res = 0;
    bool f = false;
    char temp = getchar();
    for (; !isdigit(temp); temp = getchar()) f = temp == '-';
    for (; isdigit(temp); temp = getchar()) res = res * 10 + temp - '0';
    return f ? -res : res;
}

multiset<int>s1,s2;

signed main() {
    int q = read();
    for (int i = 1; i <= q; i++) {
        int op = read();
        if (op == 1) {
            int x = read();
            s1.insert(x);

            auto item = --s1.upper_bound(x);
            auto f = item, b =item;

            if (item != s1.begin())
                s2.insert(*(--f) ^ *item);
            if (item != --s1.end())
                s2.insert(*(++b) ^ *item);
            if (item != s1.begin() && item != --s1.end())
                s2.erase(*f ^ *b);

        } else if (op == 2) {
            int x = read();

            auto item = --s1.upper_bound(x);
            auto f = item, b =item;

            if (f != s1.begin())
                s2.erase(*(--f) ^ *item);
            if (b != --s1.end())
                s2.erase(*(++b) ^ *item);
            if (item != s1.begin() && item != --s1.end())
                s2.insert(*f ^ *b);

            s1.erase(item);
        } else {
            cout << *s2.begin() << '\n';
        }
    }
    return 0;
}