#include <iostream>
#include <vector>
#include <map>
#include <algorithm>
using namespace std;

#define REP(i,s,e) for (i = s; i <= e; i++)
#define rep(i,n) REP (i,0,(int)(n)-1)
#define RREP(i,s,e) for (i = s; i >= e; i--)
#define rrep(i,n) RREP (i,(int)(n)-1,0)
#define INF (int)1e8
#define MOD (int)(1e9+7)

typedef long long ll;

int dfs(int b, vector<int>& v) {
    if (b < 0)
        return 0;
    int i;
    vector<int> s[2];
    rep (i,v.size())
        s[v[i]>>b&1].push_back(v[i]&(1<<b)-1);
    if (s[0].size() == v.size())
        return dfs(b-1,s[0]);
    else if (s[1].size() == v.size())
        return dfs(b-1,s[1]);
    else
        return min(dfs(b-1,s[0]),dfs(b-1,s[1])) + (1<<b);
}

int main(void) {
    int i, n;
    scanf("%d",&n);
    vector<int> v(n);
    rep (i,n) scanf("%d",&v[i]);

    cout << dfs(30,v) << endl;
    return 0;
}