#include<bits/stdc++.h>
using namespace std;
using ll = long long;

template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }

#define FOR(i,a,b) for(ll i=(a);i<(b);++i)
#define ALL(v) (v).begin(), (v).end()
#define p(s) cout<<(s)<<endl
#define p2(s, t) cout << (s) << " " << (t) << endl
#define br() p("")
#define pn(s) cout << (#s) << " " << (s) << endl
#define p_yes() p("Yes")
#define p_no() p("No")

const ll mod = 1e9 + 7;
const ll inf = 1e18;

template < typename T >
void vprint(T &V){
	for(auto v : V){
    	cout << v << " ";
	}
	cout << endl;
}

ll dfs(vector<ll> A, ll b){
    if(b<0){
        return 0;
    }

    vector<ll> B; // bit : 0
    vector<ll> C; // bit : 1

    for(ll a : A){
        if((a>>b) & 1){
            C.push_back(a);
        }else{
            B.push_back(b);
        }
    }
    
    if(B.size()==0 || C.size()==0){
        return dfs(A, b-1);
    }
    else{
        // bit = 1にしたとき
        ll mi0 = dfs(B, b-1) + 1LL<<b;
        ll mi1 = dfs(C, b-1) + 1LL<<b;
        return min(mi0, mi1);
    }
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    // input
    ll N;
    cin >> N;

    vector<ll> A(N);
    FOR(i, 0, N){
        cin >> A.at(i);
    }

    ll ans = dfs(A, 30);
    p(ans);

    return 0;
}