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

int n,m;
int a[100001];

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

int bitnum(int x){
  int b = x;
  int i = 0;
  while(b){
    b=b>>1;
    ++i;
  }
  return 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);
  //  printf("%d %d\n",idx,allsamebit(idx,ar));
  if(allsamebit(idx,ar)) return calc(idx-1,ar);
  else{
    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]);
    }
    //    printf("%d %d\n",calc(idx-1,one),calc(idx-1,zero));
    return (1<<idx) | min(calc(idx-1,one),calc(idx-1,zero));
  }
}

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

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