package main

import (
    "fmt"
)

func min(a int, b int) int {
    if a < b { return a }
    return b
}

func f(a []int, bit int) int {
    if (bit < 0) { return 0 }

    mask := 1 << uint(bit)

    var ones, zero []int
    for _, v := range a {
        if (mask & v) != 0 {
            ones = append(ones, v)
        } else {
            zero = append(zero, v)
        }
    }

    if len(ones) == 0 { return f(zero, bit - 1) }
    if len(zero) == 0 { return f(ones, bit - 1) }

    return mask + min(f(ones, bit - 1),
                      f(zero, bit - 1));
}

func main() {
    var n int
    fmt.Scanf("%d", &n)
    a := make([]int, n)
    for i := 0; i < n; i++ {
        fmt.Scanf("%d", &a[i])
    }
    fmt.Printf("%d\n", f(a, 30))
}