How to budget money to afford an iphone?

I want one by Christmas and I have to pay for it myself. Anyone want to do the math on how much I need per week/per day to get a $649 phone?
The phone plan isn't a cost problem, my parents are paying for it.
Don't say 'you don't need an iphone' or 'get something else.'
I also don't need you to give me phone advice.haha.
My terrible job gets me about $20 a week, because I'm currently in school.
Please help.

Added (1). I mean, I need to know how much per week. I need to know how much per week or per day so that I can choose my hours for next semester.

Added (2). GOD D*MN IT. Please just tell me how much cash I have to save per week and per day
its not that hard omg

You can't buy one then. Maybe Christmas money will be enough.

Since you make $20 a week you need to invest the $20
Try to buy candy in bulk and sell it for $1 bar/piece at your school

If it's not that hard, why the heck can a high-schooler not figure that out?

15 weeks until Christmas, means you'll need to save up $44 a week.

FYI; you're spoiled rotten.

I bought my phone from T-mobile. I paid $200 from my iPhone 5. They do not do contracts anymore so you can buy your phone in a about 12 weeks. I suggest you tell you parents to add the 11.99 insurance on the phone. That covers damage, breakage, and theft.

I would say this. You can buy an iphone for well less than that if you buy the previous version of the phone or even a version or two behind. Maybe a hundred bucks or so and you get a pretty solid phone. My 1st iphone was bought in 2007 with the flagship version which is still good and I in fact use it (although I only do so cause its cheap).

With t-mobile I pair that phone with a 30 dollar a month plan. But they have 50 dollar a month plans with data and everything that isn't bad. Depends if you live in an area where t-mobiles service is fine. Beats the hell out of a 150 dollar verizon bill and 600 dollar phone though.

If you know somebody with an iphone who's upgrading offer to buy their phone from them for like 50 bucks. Cheapest way because resellers will upcharge you where most people will almost give them away. Iphone 4 is still a fully functional device. Before you buy an old phone try to make sure your carrier will accept it though.

Edit

649 divided by 20 you stupid ***