#include <bits/stdc++.h>
using namespace std;
const int N = 1e4 + 4;
long long int a[N][20], pre[N][20], ans;
struct node {
  node *left, *right;
  long long int cnt;
  node() {
    left = NULL;
    right = NULL;
    cnt = 0;
  }
};
struct trie {
  node *x;
};
void insert(node *t, long long int x) {
  for (long long int i = 31; i >= 0; i--) {
    if (x & (1 << i)) {
      if (t->right == NULL) t->right = new node();
      t = t->right;
      t->cnt++;
    } else {
      if (t->left == NULL) t->left = new node();
      t = t->left;
      t->cnt++;
    }
  }
}
void del(node *t, long long int x) {
  for (long long int i = 31; i >= 0; i--) {
    if (x & (1 << i)) {
      t = t->right;
      t->cnt--;
    } else {
      t = t->left;
      t->cnt--;
    }
  }
}
long long int query(node *t, long long int x) {
  long long int ret = 0;
  for (long long int i = 31; i >= 0; i--) {
    if (x & (1 << i)) {
      if (t->left && t->left->cnt != 0) {
        ret |= (1 << i);
        t = t->left;
      } else
        t = t->right;
    } else {
      if (t->right && t->right->cnt != 0) {
        ret |= (1 << i);
        t = t->right;
      } else
        t = t->left;
    }
  }
  return ret;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  trie t;
  t.x = new node();
  long long int n;
  cin >> n;
  insert(t.x, 0);
  for (long long int i = 1; i <= n; i++) {
    char ch;
    cin >> ch;
    long long int x;
    cin >> x;
    if (ch == '+') insert(t.x, x);
    if (ch == '-') del(t.x, x);
    if (ch == '?') cout << query(t.x, x) << endl;
  }
  return 0;
}
