#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
#define ll long long
int n;
ll a[100000];
ll rec(int i, ll* l, ll* r){
    if(i < 0) return 0;
    ll* m = lower_bound(l, r, 1<<i, [&](ll x, ll y) -> bool { return (x&1<<i)<(y&1<<i);});
    if(m==l || m==r) return rec(i-1, l, r);
    return (1<<i) + min(rec(i-1, l, m), rec(i-1, m, r));
}

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