#include <bits/stdc++.h>
using namespace std;
#define repl(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define rep(i,n) repl(i,0,n)
#define mp(a,b) make_pair((a),(b))
#define pb(a) push_back((a))
#define all(x) (x).begin(),(x).end()
#define uniq(x) sort(all(x)),(x).erase(unique(all(x)),end(x))
#define fi first
#define se second
#define dbg(x) cout<<#x" = "<<((x))<<endl
template<class T,class U> ostream& operator<<(ostream& o, const pair<T,U> &p){o<<"("<<p.fi<<","<<p.se<<")";return o;}
template<class T> ostream& operator<<(ostream& o, const vector<T> &v){o<<"[";for(T t:v){o<<t<<",";}o<<"]";return o;}

#define INF 2147483600

int solve(int d, vector<int> &vec){//dbg(mp(d,vec));
  if(vec.size()==0) return INF;
  else if(d==0) return vec[0];
  d--;
  int n = vec.size();
  vector<int> nxt[2];
  rep(i,n) nxt[(vec[i]>>d)%2].pb(vec[i]%(1<<d));

  rep(i,2){
    if(nxt[i].size()==0) return solve(d, nxt[(i+1)%2]);
  }

  int r0 = solve(d, nxt[0]);
  int r1 = solve(d, nxt[1]);
  if(r0<r1) return r0 + (1<<d);
  else return r1 + (1<<d);
}

int main(){
  int n;
  cin>>n;
  vector<int> vec(n);
  rep(i,n) cin>>vec[i];
  int mx = *max_element(all(vec));
  int dig = 0;
  while(mx>0){dig++; mx/=2;}

  cout << solve(dig, vec) << endl;

  return 0;
}