def solve(a,i):
    if len(a) == 1:
        return 0
    b0 = []
    b1 = []
    for ai in a:
        if ai>>i&1: b1.append(ai)
        else: b0.append(ai)
    if not b0:
        return solve(b1,i-1)
    elif not b1:
        return solve(b0,i-1)
    else:
        return min(solve(b0,i-1),solve(b1,i-1)) + (1<<i)
    

n = int(input())
a = list(set(map(int,input().split())))
n = len(a)
print(solve(a,30))