from bisect import *
n = int(input())
a = sorted(map(int, input().split()))
def dfs(l, r, i):
    if i < 0:
        return 0
    for m in range(l, r):
        if (a[m]>>i)&1:
            break
    else:
        m += 1
    if m == l or m == r:
        return dfs(l, r, i-1)
    return (1<<i) + min(dfs(l, m, i-1), dfs(m, r, i-1))
print(dfs(0, n, 30))