My two friends are fight and my best friend side with one of them... what should i do?

[laughs]

Okay, there is two friends of mine, I shall name them as A and Z... my best friend was siding with A and I don't know what should I do.... cause I didn't want to side any of them... A and Z n my best friend n others friends is always tgt at sch, we eat and do everything tgt... but after A and Z fight, our clique had separate into two.... and some of my friends in clique follow Z while my best friend side with A, I had no choice but to follow my best friend to side A... but I really dun wan to side... then Z start ignoring ppl and hate ppl who is siding with A, so I was kinda ignored and it hurts if I am not with A, Z will still talk to me... but if I talk to A for like awhile, Z will ignore me afterwards.. when I talk to Z, A always looks angry n ignore me for a while... I really dun know wat I should do... its like taking a step in front is wrong, moving back a step is also wrong...until Z n her friends(friends who side Z) start bad-mouthing A at twitter..... But A didn't not badmouth them as me n my best friend tell A to tolerate it and ignore them because it makes us no different if we bad mouth them also....but things start to change... I feel like A is like using me,because when my best friend( who side with A) went home n only left me n A in school, A will then only come and find me.... but for the rest of the time in school, A just stick with my best friend.... I feel like A is using me... I think tat I have lost a bit of trust n care for A n Z.... sorry for being so long-winded.. pls pls help me to get out of this! THANKS!