#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;

//template
#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define rrep(i,a,b) for(int i=(a);i>(b);i--)
#define ALL(v) (v).begin(),(v).end()
typedef long long int ll;
const int inf = 0x3fffffff; const ll INF = 0x1fffffffffffffff; const double eps=1e-12;
void tostr(ll x,string& res){while(x)res+=('0'+(x%10)),x/=10; reverse(ALL(res)); return;}
template<class T> inline bool chmax(T& a,T b){ if(a<b){a=b;return 1;}return 0; }
template<class T> inline bool chmin(T& a,T b){ if(a>b){a=b;return 1;}return 0; }
//template end

int n;
ll dfs(vector<int> a,int bit){
   if(bit<0)return 0;
   bit--; vector<int> x,y;
   rep(i,0,a.size()){
      if(a[i]>>bit&1)x.push_back(a[i]);
      else y.push_back(a[i]);
   }
   if(x.empty()||y.empty())return dfs(a,bit);
   else return min(dfs(x,bit),dfs(y,bit))+(1<<bit);
}

int main(){
   scanf("%d",&n);
   vector<int> a(n); rep(i,0,n)scanf("%d",&a[i]);
   printf("%lld\n",dfs(a,30));
   return 0;
}