Problem
My solution : solution
I was trying to solve this problem. It asks me to print phi(n) for n=a to b(inclusive). where,

0<a<b<10^14
and b-a<10^5
My solution is,
first do sieve and save all primes <= 10^7 in a vector prm. Then, run a segmented sieve to mark which ones are prime/composite in the range [a,b]. Then do another segmented sieve to calculate phi(n) in range [a,b].
I used long long(also tried unsigned long long) almost everywhere, but i'm getting WA. Can someone give me some corner cases/reason why I may be getting WA.
Thank you.