I solved this question. Here is my submission 214189574. Now suppose, we have number of days, m = 50000 and the total number of participants = 50000(maximum limit) and suppose that an answer exists. So, the answer would be something like a worst case series like 50000 participants for day 1, 49999 participants for day 2, 49998 participants for day 3,......, 1 participants for day 50000. Then, the total number of operations performed in total days = (50000/2)*(50000+1)=1250025000 operations and as a thumb rule I remember that modern computers can perform 10^8 operations/second. So, it should take 12.5 seconds but my code is running within the 2 second time constraint. Why is this happening? Why am I not getting a TLE error?