What is that

Today i was with my friend Chun Teck from 211 taking a walk. We went up the newly build building beside the Commonwealth MRT and Queensway secondary. We decided to climb up the building not taking the lift and when we were reaching the 40 story around the 36 to 37 story i saw a indian guy half naked,he was about to wear his pants when i saw him and at the other end of the stairs, there was a girl... What are they doing, we continue climbing up and started guessing what they were doing, try guessing and tell me what you think