#include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <limits>
#include <climits>
#include <cfloat>
#include <functional>
using namespace std;

int solve(const vector<int>& a)
{
    int n = a.size();

    for(int i=30; i>=0; --i){
        vector<vector<int> > x(2);
        for(int j=0; j<n; ++j)
            x[(a[j] >> i) & 1].push_back(a[j]);
        if(x[0].size() != 0 && x[1].size() != 0)
            return (1 << i) | min(solve(x[0]), solve(x[1]));
    }
    return 0;
}

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

    cout << solve(a) << endl;

    return 0;
}