Problem Link : Here

How to approach this problem?

I got the logic to solve as:

• The no.s in the range >60 and <=n(given) which are not special(See the problem statement) has to be prime.
• So the ans would be like n — (count of primes in range [61,n])
• Would seive work Here?(as constraints are high)

I came to know about the prime no. theorem which gives the approx count of prime no.s less than x [as pi(x) = x/ln(x) or pi(x) = x/(ln(x)-1)]

Every bit of help would be appreciated ;)

Thank you so much! for giving a look to this blog.