Given two integers, LL and RR, find the maximal value of AA xor BB, where AA and BB satisfy the following condition:

L≤A≤B≤RL≤A≤B≤R

Input Format

The input contains two lines; LL is present in the first line and RR in the second line.

Constraints
1≤L≤R≤101≤L≤R≤103

Output Format

The maximal value as mentioned in the problem statement.

SAMPLE INPUT
1
10

SAMPLE OUTPUT
15

Explanation

The input tells us that L=10L=10 and R=15R=15. All the pairs which comply to above condition are the following:
10⊕10=010⊕10=0
10⊕11=110⊕11=1
10⊕12=610⊕12=6
10⊕13=710⊕13=7
10⊕14=410⊕14=4
10⊕15=510⊕15=5
11⊕11=011⊕11=0
11⊕12=711⊕12=7
11⊕13=611⊕13=6
11⊕14=511⊕14=5
11⊕15=411⊕15=4
12⊕12=012⊕12=0
12⊕13=112⊕13=1
12⊕14=212⊕14=2
12⊕15=312⊕15=3
13⊕13=013⊕13=0
13⊕14=313⊕14=3
13⊕15=213⊕15=2
14⊕14=014⊕14=0
14⊕15=114⊕15=1
15⊕15=015⊕15=0
Here two pairs (10, 13) and (11, 12) have maximum xor value 7, and this is the answer

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