HELP+Suggestions!

Hello, I need some help here!! I need to the following program but I'm stuck in the part that says "and additional 10% off for every day of the week (second day 20% of the original price and goes on)" so the user need to enter which day it is?

Here is my code so far, I just did the first part with the 10% discount but I will appreciate any suggestions or ideas!

Write a program for a boutique store that has a sale on the entire merchandise in the store. Sales are 10% off of the price on the first day and additional 10% off for every day of the week (second day 20% of the original price and goes on). A program is to be written to calculate the discount on the price of the item at the purchase time. Prompt the user for the original price.

#include <iostream.h>

int main()
{
int oprice,total;
cout<<"Enter the price of your item \$";
cin>>oprice;
total=oprice-(oprice * 0.10);
cout<<"Your total to pay is \$"<<total;
return 0;
}
(this has nothing to do with c++ as such, but)
`total = oprice - (oprice * ((NumberOfDays*10)/100) );`
`total=oprice-(oprice * 0.10);`