Sitter for the Sunday. What is this?

Lived up to its sitter status. Cracked by everyone.

p vs np, shenoyvarun86, Rogi, raklodramA, lordmaldy, krudebox, varuns88, abhijeet, bobo, akhi, Raghuvansh, Rithwik K, joe, Johny Walker, Kamal Rathi, Siddharth, anirudh patil, shyam, Dibyo, wanderlust, K.Manish, Chitananda, Atul Mathew, Gautam DN, piezocake, amarendra, Nakul, madhur, dheeraj, Wasi Manazir, sumo_ftb, superbrat, Anoop and Mo