I don't understand this sentence.... I know the meaning of all words except distinct... I looked in dictionary.. but I don't understand..:/
Output the number of distinct values when considered MOD 42, one per line for each test case.
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This is more a programming question than an English question so I suspect it will soon be closed, but for what it's worth:
As Andrew and Will note, "distinct" means "different". So the problem is saying that you are to find the set of values -- I presume where you get the "raw" set is explained earlier in the problem -- and then take each value mod 42 (i.e. the remainder when you divide by 42), and output a list of only the distinct values found, i.e. if the same number shows up more than once, only output it once.
In the specific example, you discard duplicated numbers. The number of distinct values in the set