#include <iostream>
#include <vector>

using namespace std;

typedef long long ll;
#define loop(i,a,b) for(int i=(a);i<int(b);i++)
#define rep(i,b) loop(i,0,b)

ll solve(int b, vector<ll> a){
    if(b < 0 || a.empty()) return 0;
    vector<ll> div[2];
    for(ll x : a) div[x>>b&1].push_back(x);
    if(div[0].size()==0) return solve(b-1,div[1]);
    if(div[1].size()==0) return solve(b-1,div[0]);
    ll x = solve(b-1,div[0]), y = solve(b-1,div[1]);
    return 1<<b | min(x,y);
}

int main(){
    int n;
    cin >> n;
    vector<ll> a(n);
    rep(i,n) cin >> a[i];
    cout << solve(32,a) << endl;
}