Deepak and Primes

#1

in this question we have to prime nth prime number so
that how can i recognize size of array ?

#2

@khemchandrs
N can be as large as 5000000 as per the problem constraints. The 5000000th prime number is a little over 86 million. So just take your sieve array size to be 87 million to be safe and that will work.