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Prove that in any $8$ composite positive integers not exceeding $360$, at least two are not relatively prime.
What I think is as below.
First we know there are $41$ prime numbers less than $180$, and that are all factors of $8$ composite integers, then try to find "least" $8$ composite integers then we can get a contradiction, but I do not know how to find these least $8$ composite integers.
$360$ is just $1$ less than $19^2$, so every number in $\{1,\ldots,360\}$ is either prime or divisible by a prime less than $19$, i.e. by one of $2,3,5,7,11,13,17.$ Just seven primes are here. Every one of your eight composite numbers is divisible by at least one of these seven. So use the pigeonhole principle.
