Forgot the iphone turn on password

HI, I buy iphone5 from mobile service company.

In the same time, I turned on my ihpone5 in the first time and set a password whch I turned on iphone 5 in the next time.

But I still not regular use my iphone5 in the normal time.

Today, I turned on my iphone5, But I forgot my turn on password.

Would any people help me how can I to reset my iphone turn on password ?