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

ANS=0
for i in range(32):
    x=0
    y=0

    for a in A:
        if a & (1<<i) != 0:
            x+=1
        else:
            y+=1

    if x==0 or y==0:
        True
    else:
        ANS+=1<<i

print(ANS)