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

def calc(c,A):
    if c<0:
        return 0
    
    X=[]
    Y=[]

    for a in A:
        if a & (1<<c) != 0:
            X.append(a)
        else:
            Y.append(a)

    if len(X)==0:
        return calc(c-1,Y)
    elif len(Y)==0:
        return calc(c-1,X)
    else:
        return (1<<c)+min(calc(c-1,X),calc(c-1,Y))

print(calc(32,A))