Not so Easy Math Challenge Bitmasks Competetive programmign

#1

Hi can you give me a hint or solution to solve Not so Easy Math Please Dont give me full solution or code only the idea behind it thanks.
Link:https://hack.codingblocks.com/contests/c/126/821

#2

Hi,

This question if based on inclusion exclusion principle (Set theory)
let a,b,c,d,e,f… represent set of prime numbers less than 20.

Now you have to find
a union b union c union d…

this can be found by inclusion exclusion principle.

In case you need explanation do post it.

Hit like if you get it.