#include<bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for(int i=a;i<b;i++)



#define INF INT_MAX/2
int dfs(int bit, vector<int> &v) {
    if (bit < 0) return 0;
    if (v.size() == 0) return 0;

    vector<int> v0, v1;
    for (int x : v) {
        if (x & (1 << bit)) v1.push_back(x & ((1<<bit) - 1));
        else v0.push_back(x & ((1 << bit) - 1));
    }

    if (v0.size() == v.size()) return dfs(bit - 1, v0);
    if (v1.size() == v.size()) return dfs(bit - 1, v1);

    int res = INF;
    res = min(res, dfs(bit - 1, v0));
    res = min(res, dfs(bit - 1, v1));
    res += 1 << bit;

    return res;
}
//-----------------------------------------------------------------------------------
int main() {
    int N; cin >> N;
    vector<int> v;
    rep(i, 0, N) {
        int x;
        scanf("%d", &x);
        v.push_back(x);
    }

    cout << dfs(30, v) << endl;
}