// Goで1秒かかるのかー・・・

package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func pow(x, y int) int {
	r := 1
	for i := 0; i < y; i++ {
		r *= x
	}
	return r
}

func calc(a []int, b int) int {
	if b < 0 {
		return a[0]
	}

	mask := pow(2, b)
	p0 := make([]int, 0)
	p1 := make([]int, 0)
	for i := 0; i < len(a); i++ {
		num := a[i];
		if num & mask == 0 {
			p0 = append(p0, num)
		} else {
			p1 = append(p1, num)
		}
	}

	if len(p0) == 0 {
		for i := 0; i < len(p1); i++ {
			p1[i] ^= mask;
		}
		return calc(p1, b - 1)
	} else if len(p1) == 0 {
		return calc(p0, b - 1)
	} else {
		for i := 0; i < len(p0); i++ {
			p0[i] ^= mask;
		}
		v1 := calc(p0, b - 1)
		v2 := calc(p1, b - 1)
		if v1 < v2 {
			return v1
		} else {
			return v2
		}
	}
}

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Scan(); n, _ := strconv.Atoi(sc.Text())

	a := make([]int, n)
	for i := 0; i < n; i++ {
		sc.Scan(); num, _ := strconv.Atoi(sc.Text())
		a[i] = num
	}

	fmt.Println(calc(a, 30))
}