#include <iostream>
#include <vector>
#include <cmath>
#include <map>
#include <set>
#include <iomanip>
#include <queue>
#include <algorithm>
#include <numeric>
#include <deque>
#include <complex>

using namespace std;

int f(int n, vector<int> &S){
    if (n == -1) return 0;
    vector<int> S0, S1;
    for (int i=0; i<S.size(); i++){
        if (1<<n & S[i]) S1.push_back(S[i]);
        else S0.push_back(S[i]);
    }

    if (S1.size() == 0) return f(n-1, S0);
    else if (S0.size() == 0) return f(n-1, S1);

    return min(f(n-1, S0), f(n-1, S1)) + (1<<n);
}

int main(){

    int N;
    cin >> N;
    vector<int> A(N);
    for (int i=0; i<N; i++) cin >> A[i];
    cout << f(29, A) << endl;

    return 0;
}