#include <bits/stdc++.h>
using namespace std;
int dfs(int d,vector<int> a){
	if(d<0)	return 0;
	vector<int> b,c;
	for(int i=0;i<(int)a.size();i++){
		if((a[i]>>d)%2==0)	b.push_back(a[i]);
		else 	c.push_back(a[i]);
	}
	if(b.empty()||c.empty())	return dfs(d-1,a);
	return (1<<d)+min(dfs(d-1,b),dfs(d-1,c));
}
	
int main(){
	int n;	cin>>n;
	vector<int> a(n);
	for(int i=0;i<n;i++)	cin>>a[i];
	cout<<dfs(30,a)<<endl;
	return 0;
}