#include <bits/stdc++.h>
struct Trie {
  Trie* c[2];
  int st;
  Trie() : st(0) { c[0] = c[1] = NULL; }
  void add(int x, int d) {
    ++st;
    if (d == -1) return;
    if (c[((1 << d) & x) != 0] == NULL) c[((1 << d) & x) != 0] = new Trie();
    c[((1 << d) & x) != 0]->add(x, d - 1);
  }
  void del(int x, int d) {
    --st;
    if (d != -1) {
      c[((1 << d) & x) != 0]->del(x, d - 1);
      if (c[((1 << d) & x) != 0]->st == 0) {
        delete c[((1 << d) & x) != 0];
        c[((1 << d) & x) != 0] = NULL;
      }
    }
  }
  int q(int x, int d) {
    if (d == -1) return 0;
    if (c[(((1 << d) & x) != 0) ^ 1] != NULL)
      return c[(((1 << d) & x) != 0) ^ 1]->q(x, d - 1) | (1 << d);
    else
      return c[((1 << d) & x) != 0]->q(x, d - 1);
  }
};
Trie trie;
int trielen;
int main() {
  int q, x;
  char op;
  scanf("%d", &q);
  trie.add(0, 30);
  while (q--) {
    scanf(" %c %d", &op, &x);
    switch (op) {
      case '+':
        trie.add(x, 30);
        break;
      case '-':
        trie.del(x, 30);
        break;
      case '?':
        printf("%d\n", trie.q(x, 30));
        break;
    }
  }
  return 0;
}
