How to tell if my iphone has been jail broken?

I bought my iphone 4 new from sprint

Umm if its new then its not jailbroken, look for an app called "Cydia"… No Cydia = no jailbreak… Cydia=jailbrek

If it doesn't work u idiot you just lost everything your phone is worth u dumb b***!

It will have an app called cydia n your app store shouldn't work but if its new it shouldn't be jailbroken