#include <bits/stdc++.h>

#define pb push_back
#define mp make_pair
#define sz size
#define ll long long
#define ld long double
#define fs first
#define sc second
#define forn(i, f, t) for(int i = f; i < t; i++)
#define all(x) (x).begin(), (x).end()
#define ins insert

const int INF = 2147483647;
const int MOD = 1000000007;
const ll INF64 = 9223372036854775807;
const ld EPS = 1e-7;

using namespace std;

struct node{
    int next[2];
    int isFinal;
} ar[1000001];

int cnt = 0;

void add(int x){
    int cur = 0;
    for (int i = 30; i >= 0; i--)
        if (ar[cur].next[x & (1 << i) ? 1 : 0] != -1){
            cur = ar[cur].next[x & (1 << i) ? 1 : 0];
            ar[cur].isFinal++;
        }
        else{
            ar[cur].next[x & (1 << i) ? 1 : 0] = ++cnt;
            cur = ar[cur].next[x & (1 << i) ? 1 : 0];
            ar[cur].isFinal = 1;
            ar[cur].next[0] = ar[cur].next[1] = -1;
        }
}


void rem(int x){
    int cur = 0;
    for (int i = 30; i >= 0; i--){
        cur = ar[cur].next[x & (1 << i) ? 1 : 0];
        ar[cur].isFinal--;
    }
}


int find(int x){
    int cur = 0, tmp = 0;
    for (int i = 30; i >= 0; i--)
        if (ar[cur].next[x & (1 << i) ? 0 : 1] != -1 && ar[ar[cur].next[x & (1 << i) ? 0 : 1]].isFinal){
            tmp += (1 << i);
            cur = ar[cur].next[x & (1 << i) ? 0 : 1];
        }
        else
            cur = ar[cur].next[x & (1 << i) ? 1 : 0];
    return tmp;
}


int main(){
    int n, x;
    scanf("%d", &n);
    char c;
    ar[0].next[0] = -1;
    ar[0].next[1] = -1;
    ar[0].isFinal = 0;
    forn(i, 0, n){
        scanf("\n%c %d", &c, &x);
        if (c == '+') add(x);
        else if (c == '-') rem(x);
        else if (c == '?') printf("%d\n", find(x));
    }

    return 0;
}