CF1493E Enormous XOR

You are given two integers $ l $ and $ r $ in binary representation. Let $ g(x, y) $ be equal to the [bitwise XOR](https://en.wikipedia.org/wiki/Bitwise_operation#XOR) of all integers from $ x $ to $ y $ inclusive (that is $ x \oplus (x+1) \oplus \dots \oplus (y-1) \oplus y $ ). Let's define $ f(l, r) $ as the maximum of all values of $ g(x, y) $ satisfying $ l \le x \le y \le r $ . Output $ f(l, r) $ .

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In sample test case $ l=19 $ , $ r=122 $ . $ f(x,y) $ is maximal and is equal to $ 127 $ , with $ x=27 $ , $ y=100 $ , for example.