#!/usr/bin/python3
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# https://www.hackerrank.com/challenges/maximizing-xor
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import sys
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def max_xor(L,R):
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res = 1
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n = L ^ R
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while n > 0:
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n >>=1
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res <<= 1
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return res - 1
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def main():
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L = int(sys.stdin.readline())
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R = int(sys.stdin.readline())
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print(max_xor(L,R))
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if __name__ == '__main__':
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main()
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