#include <bits/stdc++.h>
using namespace std;
const int maxn = 3 * 1e6 + 7;
struct Tree {
  int Next[maxn][2];
  int val[maxn];
  int L, root;
  void init() {
    L = 0;
    root = newnode();
  }
  int newnode() {
    for (int i = 0; i < 2; i++) Next[L][i] = -1;
    val[L++] = 0;
    return L - 1;
  }
  void insert(int va) {
    int u = root, v;
    for (int i = 29; i >= 0; i--) {
      v = (va & (1 << i)) ? 1 : 0;
      if (Next[u][v] == -1) Next[u][v] = newnode();
      u = Next[u][v];
      val[u]++;
    }
  }
  void Delete(int va) {
    int u = root, v;
    for (int i = 29; i >= 0; i--) {
      v = (va & (1 << i)) ? 1 : 0;
      u = Next[u][v];
      val[u]--;
    }
  }
  int query(int x) {
    int u = root, v;
    for (int i = 29; i >= 0; i--) {
      v = (x & (1 << i)) ? 1 : 0;
      if (v == 1) {
        if (Next[u][0] != -1 && val[Next[u][0]])
          u = Next[u][0];
        else {
          u = Next[u][1];
          x ^= (1 << i);
        }
      } else {
        if (Next[u][1] != -1 && val[Next[u][1]]) {
          u = Next[u][1];
          x ^= (1 << i);
        } else
          u = Next[u][0];
      }
    }
    return x;
  }
} T;
int main() {
  int q;
  T.init();
  T.insert(0);
  scanf("%d", &q);
  while (q--) {
    string op;
    int v;
    cin >> op >> v;
    if (op == "+") T.insert(v);
    if (op == "-") T.Delete(v);
    if (op == "?") printf("%d\n", T.query(v));
  }
}
