Debts

Alice currently has $a$ hryvnias. She remembers that Petro owes her $b$ hryvnias and Svitlana owes her $c$ hryvnias. However, Alice owes Romchik $d$ hryvnias.

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

Input

The first line contains one integer $a$ ($1\le a\le 100$) — the number of hryvnias Alice has.

The second line contains one integer $b$ ($1\le b\le 100$) — the number of hryvnias that Petro owes Alice.

The third line contains one integer $c$ ($1\le c\le 100$) — the number of hryvnias that Svitlana owes Alice.

The fourth line contains one integer $d$ ($1\le d\le 100$) — the number of hryvnias that Alice owes Romchik.

It is guaranteed that Alice will have a non-negative amount of hryvnias in the end.

Output

Output one integer — the answer to the problem.

Examples