import sys
#input = sys.stdin.readline
#input = sys.stdin.buffer.readline #文字列はダメ
#sys.setrecursionlimit(1000000)
#import math
#import bisect
#import itertools
#import random
#from heapq import heapify, heappop, heappush
from collections import defaultdict
from collections import deque
import copy #DeepCopy: hoge = [_[:] for _ in hogehoge]
#from functools import lru_cache
#@lru_cache(maxsize=None)
MOD = pow(10,9) + 7
#MOD = 998244353
dx = [1,0,-1,0]
dy = [0,1,0,-1]
#dx8 = [1,1,0,-1,-1,-1,0,1]
#dy8 = [0,1,1,1,0,-1,-1,-1]

def main():
    Q = int(input())
    MX = 32
    S = set([])
    num = [0]*MX
    ans = 0
    for _ in range(Q):
        query = str(input())
        if len(query) == 1:
            if len(S) == 0:
                print(-1)
            else:
                print(ans)
        else:
            x = int(query[2:])
            if int(query[0]) == 1:
                if x in S:
                    continue
                S.add(x)
                for i in range(MX):
                    if (x>>i)&1 == 1:
                        num[i] += 1
            else:
                if x not in S:
                    continue
                S.remove(x)
                for i in range(MX):
                    if (x>>i)&1 == 1:
                        num[i] -= 1
            # print(S,num)
            ans = 0
            for i in range(MX):
                if num[i] == len(S):
                    ans += 1<<i


if __name__ == '__main__':
    main()