#include <bits/stdc++.h>
using namespace std;

typedef long long   signed int LL;
typedef long long unsigned int LU;

#define incID(i, l, r) for(int i = (l)    ; i <  (r); i++)
#define incII(i, l, r) for(int i = (l)    ; i <= (r); i++)
#define decID(i, l, r) for(int i = (r) - 1; i >= (l); i--)
#define decII(i, l, r) for(int i = (r)    ; i >= (l); i--)
#define  inc(i, n) incID(i, 0, n)
#define inc1(i, n) incII(i, 1, n)
#define  dec(i, n) decID(i, 0, n)
#define dec1(i, n) decII(i, 1, n)

#define inII(v, l, r) ((l) <= (v) && (v) <= (r))
#define inID(v, l, r) ((l) <= (v) && (v) <  (r))

#define PB push_back
#define EB emplace_back
#define MP make_pair
#define FI first
#define SE second
#define UB upper_bound
#define LB lower_bound
#define PQ priority_queue

#define  ALL(v)  v.begin(),  v.end()
#define RALL(v) v.rbegin(), v.rend()
#define  FOR(it, v) for(auto it =  v.begin(); it !=  v.end(); ++it)
#define RFOR(it, v) for(auto it = v.rbegin(); it != v.rend(); ++it)

template<typename T> bool   setmin(T & a, T b) { if(b <  a) { a = b; return true; } else { return false; } }
template<typename T> bool   setmax(T & a, T b) { if(b >  a) { a = b; return true; } else { return false; } }
template<typename T> bool setmineq(T & a, T b) { if(b <= a) { a = b; return true; } else { return false; } }
template<typename T> bool setmaxeq(T & a, T b) { if(b >= a) { a = b; return true; } else { return false; } }
template<typename T> T gcd(T a, T b) { return (b == 0 ? a : gcd(b, a % b)); }
template<typename T> T lcm(T a, T b) { return a / gcd(a, b) * b; }

// ---- ----

int n, a[100000];

int f(int d, int l, int r) {
	if(l == r) { return -1; }
	if(d == 0) { return  0; }
	int m = l;
	while(m < r && (a[m] >> (d - 1)) % 2 == 0) { m++; }
	int x = f(d - 1, l, m);
	int y = f(d - 1, m, r);
	// printf("%2d:  [%d, %d): %d, [%d, %d): %d\n", d - 1, l, m, x, m, r, y);
	
	if(max(x, y) == -1) { return 0; }
	else if(min(x, y) == -1) { return max(x, y); }
	else { return (1 << (d - 1)) + min(x, y); }
}

int main() {
	cin >> n;
	inc(i, n) { cin >> a[i]; }
	
	sort(a, a + n);
	int p = 0;
	inc(i, n) {
		while(! (p == n || p == 0 || a[p] != a[p - 1])) { p++; }
		if(p < n) { a[i] = a[p++]; }
		if(p == n) { n = i; break; }
	}
	// inc(i, n) { cout << a[i] << " "; } cout << endl;
	
	cout << f(30, 0, n) << endl;
	
	return 0;
}