B - Johnny and His Hobbies

#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
const int maxn=1050;
int ah[maxn];
int bh[maxn];
int main(){
    int t;
    scanf("%d",&t);
    while(t--){
        int n;
        int flag = 1;
        int k;
        scanf("%d", &n);
        for (int i = 1; i <= n;i++){
            scanf("%d", &ah[i]);
        }
        sort(ah + 1, ah + 1 + n);
        for (int i = 1; i <= 1024;i++){
            flag = 1;
            for (int j = 1; j <= n;j++){
                bh[j] = ah[j] ^ i;
            }
            sort(bh + 1, bh + 1 + n);
            for (int j = 1; j <= n;j++){
                if(bh[j]!=ah[j]){
                    flag = 0;
                    break;
                }
            }
           if(flag){
               k = i;
               break;
           }
               
        }
        if(flag)
            printf("%d\n", k);
        else
            printf("-1\n");
    }
}