#include <cstdio>
#include <algorithm>
#include <vector>
using namespace std;

int n;
int a[100001];

void input(){
  scanf("%d",&n);
  for(int i=0;i<n;++i) scanf("%d",a+i);
}

int ibit(int idx,int num){
  return (num>>idx) & 1;
}

bool allsamebit(int idx,vector<int> ar){
  bool one = true,zero = true;
  int n = ar.size();
  for(int i=0;i<n;++i){
    if(ibit(idx,ar[i])) zero = false;
    else one = false;
  }
  return one||zero;
}
int calc(int idx,vector<int> ar){
  if(ar.size()<=1) return 0;
  if(idx==0) return !allsamebit(idx,ar);
  
  vector<int> one,zero; //set of ith bit is 1/0
  int n = ar.size();
  for(int i=0;i<n;++i){
    if((ar[i]>>idx) & 1) one.push_back(ar[i]);
    else zero.push_back(ar[i]);
  }

  if(one.size()==0) return calc(idx-1,zero);
  if(zero.size()==0) return calc(idx-1,one);
  return (1<<idx) | min(calc(idx-1,one),calc(idx-1,zero));
}

void solve(){
  sort(a,a+n);
  vector<int> ar;
  ar.push_back(a[0]);
  for(int i=1;i<n;++i) if(a[i]!=a[i-1]) ar.push_back(a[i]);
  printf("%d\n",calc(30,ar));
}

int main(){
  input();
  solve();
  return 0;
}