#include <bits/stdc++.h>
using namespace std;
struct node {
  int freq;
  node *next[2];
  node() {
    freq = 0;
    for (int i = 0; i < 2; i++) {
      next[i] = NULL;
    }
  }
} * root;
void insert(int n, int val) {
  node *cur = root;
  for (int i = 31; i >= 0; i--) {
    int id = (n & (1 << i));
    id = id >> i;
    if (cur->next[id] == NULL) {
      cur->next[id] = new node();
    }
    cur = cur->next[id];
    cur->freq += val;
  }
}
int search(int n) {
  node *cur = root;
  int ans = 0;
  for (int i = 31; i >= 0; i--) {
    int id = n & (1 << i);
    id = id >> i;
    if (cur->next[id ^ 1] && cur->next[id ^ 1]->freq) {
      ans += (1 << i);
      cur = cur->next[id ^ 1];
    } else {
      cur = cur->next[id];
    }
  }
  return ans;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int i, j, k, l, m, n, p, q;
  char c;
  cin >> n;
  root = new node();
  insert(0, 1);
  for (i = 0; i < n; i++) {
    cin >> c >> p;
    if (c == '+') {
      insert(p, 1);
    } else if (c == '-') {
      insert(p, -1);
    } else {
      cout << search(p) << endl;
    }
  }
  return 0;
}
