Prime visits tle exceeded

#1

I wrote almost correct code but not able to figure out what i missed because of which I am getting TLE in 3rd ccase. ANd what is the fastest way to find prime no.
ide link: https://ide.codingblocks.com/s/113414

#2

hey @piyush.bansal8158625, as contraints are high in the question, use prime seive approach to calculate prime numbers