Because not only was he teasing me right from durbarmarg all the way till sorakhutte he was also using some offensive word like 'randi#%*'. When I seemed to notice, he and his friend at front who was riding the scooter speeded up. I followed their speed and luckily vechiles were stopped on a diversion lane on sorakhutte chowk. I could not wait any longer to teach them a lesson. They looked terrified and shocked once I stopped my scooty right middle of jam and went towards them. I slapped him, the one sitting at back. 
Traffic police came for inspection/rescue/enquiry and told us to park our scooters. I told them everything and the guy was denying the fact. But I was damn sure that they were teasing me, looking at my thighs, staring at me and making me feel uncomfortable. I was pulling my t-shirt right then after they started giggling and saying words at durbarmarg and at that very moment I could have met with an accident because I was riding only with one hand and pulling my t-shirt down by the other. I told everything to police. Those guys were to be sent to police station. The one whom I slapped was begging to forgive that he was an IT student and had exams. I forgived them after they caught their ears and said sorry to me three times and promised never to do it again.