#include<stdio.h>
int a[100000];
int b[100000];
int min(int a,int b){return a<b?a:b;}

int solve(int l,int r,int d){
	if(d==-1)return 0;
	int i;
	int p=l;
	for(i=l;i<r;i++)if(!(a[i]>>d&1))b[p++]=a[i];
	int mid=p;
	for(i=l;i<r;i++)if(a[i]>>d&1)b[p++]=a[i];
	for(i=l;i<r;i++)a[i]=b[i];
	if(mid==l||mid==r)return solve(l,r,d-1);
	int vl=solve(l,mid,d-1);
	int vr=solve(mid,r,d-1);
	return min(vl,vr)+(1<<d);
}

int main(){
	int n,i;
	scanf("%d",&n);
	for(i=0;i<n;i++)scanf("%d",&a[i]);
	printf("%d\n",solve(0,n,30));
	return 0;
}