#include<bits/stdc++.h>
using namespace std;
#define fs first
#define sc second
#define pb push_back
#define mp make_pair
#define eb emplace_back
#define ALL(A) A.begin(),A.end()
#define RALL(A) A.rbegin(),A.rend()
typedef long long LL;
typedef pair<LL,LL> P;
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<typename T> T gcd(T a,T b){return b?gcd(b,a%b):a;}
const LL mod=1000000007;
const LL LINF=1LL<<62;
const int INF=1<<30;
int dx[]={1,0,-1,0,1,-1,1,-1};
int dy[]={0,1,0,-1,1,-1,-1,1};
 
LL rec(int k,vector<LL> a){
    if(k==-1) return 0;
    int n = a.size();
    bool z = false,o = false;
    for (int i = 0; i < n; i++) {
        if((a[i]>>k)&1) o = true;
        else z = true;
    }
    if(!o){
        return rec(k-1,a);
    }
    else if(!z){
        for (int i = 0; i < n; i++) {
            a[i] ^= 1LL << k;
        }
        return rec(k-1,a);
    }
    else{
        vector<LL> p,q;
        for (int i = 0; i < n; i++) {
            if((a[i] >> k)&1) p.pb(a[i] ^ (1LL << k));
            else q.pb(a[i]);
        }
        return min(rec(k-1,p), rec(k-1,q)) + (1LL << k);
    }
}
 
 
int main(){
    int n;cin >> n;
    vector<LL> a(n);
    int k = 0;
    for (int i = 0; i < n; i++) {
        scanf("%lld",&a[i]);
        LL t = a[i];
        int cnt = 0;
        while(t){
            t >>= 1;
            cnt++;
        }
        k = max(k, cnt);
    }
    cout << rec(k,a) << endl;
    return 0;
}