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

int solve(vector<int>& nums, int bit) {
    if (bit < 0) return 0;
    
    vector<int> zero, one;
    for (int num : nums) {
        if (num & (1 << bit)) {
            one.push_back(num);
        } else {
            zero.push_back(num);
        }
    }
    
    if (zero.empty()) return solve(one, bit - 1);
    if (one.empty()) return solve(zero, bit - 1);
    
    return min(solve(zero, bit - 1), solve(one, bit - 1)) + (1 << bit);
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    
    int n;
    cin >> n;
    vector<int> a(n);
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }
    
    int ans = solve(a, 30);
    cout << ans << "\n";
    
    return 0;
}