In this problem, we have to find the nearest prime number smaller than N and greater than N. (3 <= N <= 2^32). I have used Miller Rabin but it’s showing TLE. Similar problem: http://www.spoj.pl/problems/PAGAIN/
You need Sieve of Eratosthenes algorhitm. you can this view here:
a better Sieve approach. https://github.com/cacophonix/SPOJ/blob/master/PAGAIN.cpp