# Debts

Execution time limit is 1 second

Runtime memory usage limit is 256 megabytes

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 $a$ ($1≤a≤100$) — the number of hryvnias Alice has.

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

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

The fourth line contains one integer $d$ ($1≤d≤100$) — 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

Input #1

Answer #1

Input #2

Answer #2

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