def greedy(A,B):
    Z=-1; T=[]
    for x in range(A+1):
        for y in range(B+1):
            if min(x,y,x^y)>Z:
                Z=min(x,y,x^y)
                T=[(x,y,Z)]
            elif min(x,y,x^y)==Z:
                T.append((x,y,Z))
    return T

def solve(A,B):
    a=A.bit_length(); b=B.bit_length()
    if a==b:
        return (1<<(a-1))-1
    else:
        return min(A,B)

A,B=map(int,input().split())
print(solve(A,B))