n = int(input())
A = list(set(map(int, input().split())))

def dfs(A, t):
    if len(A) == 1 or t == -1:
        return 0

    L = []
    R = []
    for a in A:
        if a >> t & 1:
            L.append(a ^ (1 << t))
        else:
            R.append(a)
    if L and R:
        return min(dfs(L, t - 1), dfs(R, t - 1)) | (1 << t)
    elif L:
        return dfs(L, t - 1)
    else:
        return dfs(R, t - 1)

print(dfs(A, 29))