'''
Yuki130
No.130 XOR Minimax
'''
from collections import deque
from bisect import bisect_left

N = int(input())
A = list(map(int, input().split()))
A.sort()
amax = max(A)
n = amax.bit_length() - 1
q = deque()  # target,left,right,value
q.append((2 ** n, n, 0, N, 0))
ans = 10 ** 10
while len(q) > 0:
    (x, i, l, r, v) = q.pop()
    if i < 0:
        if ans > v:
            ans = v
        continue
    y = bisect_left(A, x)
    if y == l:
        q.append((x + 2 ** (i - 1), i - 1, y, r, v * 2))
    elif y == r:
        q.append((x - 2 ** (i - 1), i - 1, l, y, v * 2))
    else:
        q.append((x + 2 ** (i - 1), i - 1, y, r, v * 2 + 1))
        q.append((x - 2 ** (i - 1), i - 1, l, y, v * 2 + 1))
print(ans)