3 6 1 4 3
1
There are two good sets: {$2,3$} and {$1,2,3$}.
Card $1$ is only contained in {$1,2,3$}, and this set without card $1$, {$2,3$}, is also good. Thus, card $1$ is unnecessary.
For card $2$, a good set {$2,3$} without card $2$, {$3$}, is not good. Thus, card $2$ is NOT unnecessary.
Neither is card $3$ for a similar reason, hence the answer is $1$.5 400 3 1 4 1 5
5 In this case, there is no good set. Therefore, all the cards are unnecessary.
6 20 10 4 3 10 25 2
3
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