a,b=map(int,input().split())

if a>b:
    tmp=a
    a=b
    b=tmp

def two_digit(x):
    result=0
    while(x>0):
        x//=2
        result+=1
    return result

a_digit=two_digit(a)
b_digit=two_digit(b)

if a_digit==b_digit:
    ans=2**(a_digit-1)-1
else:
    ans=a
print(ans)