Chef And Partytions

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Chef is hosting a party. There are $2N$ people in this party (excluding Chef). Each person has a unique ID $i$ which ranges from $1$ to $2N$. Chef wants to make $N$ pairs of the $2N$ people (that is, each pair should contain $2$ people). A pair of people $(i,j)$ will be sad if $\gcd(i,j)=1$. Chef wants to minimize the number of sad pairs. Can you help him find the minimum number of sad pairs and

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solution.cppC++17

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