参考答案：

#include<iostream>

using namespace std;

const int N = 100010, M = 31 * N;
int son[M][2], a[N], idx;

void insert(int x)
{
    int p = 0;
    for (int i = 30; i >= 0; --i)
    {
        int u = x >> i & 1;
        if (!son[p][u]) son[p][u] = ++idx;
        p = son[p][u];
    }
}
int query(int x)
{
    int p = 0;
    int res = 0;

    for (int i = 30; i >= 0; --i)
    {
        int u = x >> i & 1;
        if (son[p][!u])
        {
            p = son[p][!u];
            res = res * 2 + 1;
        }
        else
        {
            p = son[p][u];
            res = res * 2 + 0;
        }
    }

    return res;
}
int main()
{
    int n, res = 0;

    cin >> n;
    for (int i = 0; i < n; ++i)
    {
        cin >> a[i];
        insert(a[i]);
    }

    for (int i = 0; i < n; ++i) res = max(res, query(a[i]));
    cout << res << endl;

    return 0;
}