#include <bits/stdc++.h>
using namespace std;
using ll = long long;
template<class T,class U> using P = pair<T,U>;
template<class T> using vec = vector<T>;
template<class T> using vvec = vector<vec<T>>;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N;
    cin >> N;
    vec<ll> A(N);
    int h = 0;
    for(int i=0;i<N;i++){
        cin >> A[i];
        for(int j=0;j<30;j++) if(A[i]&(1<<j)) h = j;
    }

    auto calc = [&](auto&& self,vec<ll> A,int bit)->ll{
        bool ok = true;
        int n = A.size();
        if(n<=1 || bit<0) return 0;
        vec<ll> X,Y;
        for(int i=0;i<n;i++){
            if(A[i]&(1<<bit)) X.push_back(A[i]%(1<<bit));
            else Y.push_back(A[i]%(1<<bit));
        }
        if(X.empty() || Y.empty()) return (X.empty()? self(self,Y,bit-1):self(self,X,bit-1));
        else return (1<<bit) + min(self(self,X,bit-1),self(self,Y,bit-1));
    };
    cout << calc(calc,A,h) << endl;
}