#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint1000000007;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000000

int get(vector<int> a,int b){
	if(a.size()==0)return 0;
	if(b==-1)return 0;
	vector<vector<int>> x(2);
	rep(i,a.size()){
		if((a[i]>>b)&1){
			x[1].push_back(a[i]^(1<<b));
		}
		else{
			x[0].push_back(a[i]);
		}
	}
	if(x[0].size()==0||x[1].size()==0){
		return max(get(x[0],b-1),get(x[1],b-1));
	}
	else{
		return min(get(x[0],b-1),get(x[1],b-1)) + 1<<b;
	}
}

int main(){
	
	int N;
	cin>>N;
	
	vector<int> a(N);
	rep(i,N)cin>>a[i];
	
	cout<<get(a,30)<<endl;
	
	return 0;
}