Alice now has a hryvnias. She remembers that Petya owes her b hryvnias, Svetlana owes her c hryvnias. However, Alice owes Roma d hryvnia.

If everyone repays their debts, how many hryvnias will Alice have?

Input

The first line contains one integer a (1 ≤ a ≤ 100) - the amount of hryvnias that Alice has.

The second line contains a single integer b (1 ≤ b ≤ 100) - the amount of hryvnia that Petya owes Alisa.

The third line contains a single integer c (1 ≤ c ≤ 100) - the amount of hryvnia that Svetlana owes Alisa.

The fourth line contains a single integer d (1 ≤ d ≤ 100) - the amount of hryvnias that Alisa owes Roma.

It is guaranteed that Alice will end up with a non-negative amount of hryvnias.

Output

Print one integer - the amount of hryvnias that Alice will have.