#!/usr/bin/env python3.8
# %%
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines


# %%
N, *A = map(int, read().split())

# %%


def solve(A, n):
    if len(A) == 1:
        return 0
    bit = 1 << n
    A0 = [x for x in A if not (x & bit)]
    A1 = [x ^ bit for x in A if x & bit]
    if not A0:
        return solve(A1, n - 1)
    elif not A1:
        return solve(A0, n - 1)
    else:
        return bit + min(solve(A0, n - 1), solve(A1, n - 1))


# %%
print(solve(set(A), 30))