#include <iostream>
#include <algorithm>
using namespace std;

int n, a[100005];

int func(int k, int l, int r){
    if(k == -1) return 0;
    int m = r;
    for(int i = l; i < r; ++i){
        if(a[i] >> k & 1) { m = i; break; }
    }
    int res = 1001001001;
    if(l < m)   res = min(res, func(k - 1, l, m));
    if(m < r)   res = min(res, func(k - 1, m, r));
    if(l < m && m < r)  res += 1 << k;
    return res;
}

int main(){
    cin >> n;
    for(int i = 0; i < n; ++i)  cin >> a[i];
    sort(a, a + n);
    cout << func(30, 0, n) << endl;
    return 0;
}