import sys
sys.setrecursionlimit(10**6)
n = int(input())
a = list(map(int,input().split()))

c=[[0,0] for i in range(31)]
for i in a:
    t=bin(i)[2:][::-1]
    for j in range(len(t)):
        c[j][int(t[j])] += 1

cnt = 0
for i,j in c:
    if i + j == 0:
        break
    cnt+=1

lis=[]
def  cal(x,ind):
    if ind == cnt:
        lis.append(int(x[::-1],2))
        return
    o,i=c[ind][0],c[ind][1]
    
    if o == n:
        cal(x+'0',ind+1)
    elif i == n:
        cal(x+'1',ind+1)
    else:
        cal(x+'0',ind+1)
        cal(x+'1',ind+1)
        
cal('',0)
A=10**18
for x in lis:
    t=0
    for i in a:
        t=max(i^x,t)
    A=min(A,t)
    
print(A)