import sys
readline=sys.stdin.readline

N=int(readline())
A=list(map(int,readline().split()))
def solve(A,bit):
    if bit==0:
        if len(set(A))>=2:
            return 1
        else:
            return 0
    A0,A1=[],[]
    for a in A:
        if a&1<<bit:
            A1.append(a^1<<bit)
        else:
            A0.append(a)
    if A0 and A1:
        return min(solve(A0,bit-1),solve(A1,bit-1))|1<<bit
    else:
        return solve(A,bit-1)
ans=solve(A,30)
print(ans)