Problem Statement
Takahashi threw three dice, and they showed three numbers aa, bb, and cc.
If there are two same numbers among aa, bb, and cc, print the remaining number. Otherwise, print 00.
Constraints
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1 \leq a,b,c \leq 61≤a,b,c≤6
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All of aa, bb, and cc are integers.
Input
Input is given from Standard Input in the following format:
aabbcc
Output
If there are two same numbers among aa, bb, and cc, print the remaining number. Otherwise, print 00.