#include <bits/stdc++.h>
using namespace std;
int q, x;
char c;
struct trie {
  int cunt;
  trie *one, *zer;
  trie() {
    cunt = 0;
    one = zer = 0;
  }
};
int get_count(trie *t) {
  if (t == 0) return 0;
  return t->cunt;
}
void add(trie *t, int num, int bit, int test) {
  t->cunt += test;
  if (bit == -1) return;
  if (num & (1 << bit)) {
    if (get_count(t->one) == 0) t->one = new trie();
    add(t->one, num, bit - 1, test);
  } else {
    if (get_count(t->zer) == 0) t->zer = new trie();
    add(t->zer, num, bit - 1, test);
  }
}
int sol(trie *t, int num, int bit) {
  if (bit == -1) return 0;
  if (num & (1 << bit)) {
    if (get_count(t->zer) != 0) return (1 << bit) + sol(t->zer, num, bit - 1);
    return sol(t->one, num, bit - 1);
  } else {
    if (get_count(t->one) != 0) return (1 << bit) + sol(t->one, num, bit - 1);
    return sol(t->zer, num, bit - 1);
  }
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  trie *t = new trie();
  add(t, 0, 31, 1);
  cin >> q;
  while (q--) {
    cin >> c >> x;
    if (c == '+') add(t, x, 31, 1);
    if (c == '-') add(t, x, 31, -1);
    if (c == '?') cout << sol(t, x, 31) << endl;
  }
  return 0;
}
