N = int(input())
lsa = list(map(int,input().split()))

def dfs(ls,p):
    if p < 0:
        return 0
    A = []
    B = []
    T = ls[:]
    for j in T:
        if (j >> p) % 2 == 0:
            A.append(j)
        else:
            B.append(j)
    ans = 0
    if (len(A) == 0) or (len(B) == 0):
        ans = dfs(T,p-1)
    else:
        ans = dfs(A,p-1)
        ans = min(ans,dfs(B,p-1))
        ans += 1 << p
    return ans

print(dfs(lsa,30))