It was SunG by Papon

If the three songs from Cirkus in my collection were arranged in the alphabetical order, Sun Zara was the last.

And if they were arranged in the ascending order of their durations (or the descending order, if you please), it would be the second – it was three minutes and 35 seconds long.

There were a couple of reasons for people complying with the instruction suggested by the title of the song – the two people who sang it, Shreya Ghoshal and Papon.

It was written by Kumaar, and was composed by Devi Sri Prasad (a.k.a. DSP).