#include <iostream>

using namespace std;
int rec[10000005][2];

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int amount, n;
    int cnt = 0;
    cin >> amount;

    int result = 0;
    for (int i = 0; i < amount; i++) {
        cin >> n;
        int insert_p = 0;
        int search_p = 0;
        int val = 0;
        int bits = 30;
        while (bits >= 0) {
            int head = n >> bits & 1;
            if (rec[insert_p][head] == 0) {
                rec[insert_p][head] = ++cnt;
            }
            insert_p = rec[insert_p][head];

            if (rec[search_p][1 - head] != 0) {
                search_p = rec[search_p][1 - head];
                val += 1 << bits;
            } else {
                search_p = rec[search_p][head];
            }
            bits--;
        }
        if (val > result) { result = val; }
    }

    cout << result;
    return 0;
}

insert 和 search 可以一个循环一起完成