is it ok for me and guys in their 20s to have fist fight with me?

there is a guy who is in his 20s and he keeps trying to scare me by calling me and asking my name and he will be with other 2 boys. if he suddenly starts punching me, should i also punch him or run away? i am 15 yr old boy. i always run away from them. that guy is 6' tall, another is also nearly 6' and the 3rd one is 5'10 and i am 5'7 3/4".....