Saving Taxes

In Chefland, everyone who earns **strictly** more than $Y$ rupees per year, has to pay a tax to Chef. Chef has allowed a special scheme where you can invest any amount of money and claim exemption for it. You have earned $X$ $(X \gt Y)$ rupees this year. Find the **minimum** amount of money you have to invest so that you don't have to pay taxes this year. ### Input - The first line of input will