If you know some special features of special data limit,you can find some way that others don't know but is able to pass the test and can't be hacked.↵
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# 1.Addition limits feature↵
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For $a_i \existsin N,\sum a_i \le W$,it's sure that there are at most $\sqrt W$ distinct number in array $a_i$.↵
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For some strings problem,there are limits of the total length of strings $M$,as those strings have at most $\sqrt M$ distinct length.↵
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example:
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# 1.Addition limits feature↵
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For $a_i \
↵
For some strings problem,there are limits of the total length of strings $M$,as those strings have at most $\sqrt M$ distinct length.↵
↵
example:
