﻿ ABC167 B - Easy Linear Programming - Atcoder

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Score : $200$ points

### Problem Statement

We have $A$ cards, each of which has an integer $1$ written on it. Similarly, we also have $B$ cards with $0$s and $C$ cards with $-1$s.

We will pick up $K$ among these cards. What is the maximum possible sum of the numbers written on the cards chosen?

### Constraints

• All values in input are integers.
• $0 \leq A, B, C$
• $1 \leq K \leq A + B + C \leq 2 \times 10^9$

### Input

Input is given from Standard Input in the following format:

$A$ $B$ $C$ $K$


### Output

Print the maximum possible sum of the numbers written on the cards chosen.

### Sample Input 1

2 1 1 3


### Sample Output 1

2


Consider picking up two cards with $1$s and one card with a $0$. In this case, the sum of the numbers written on the cards is $2$, which is the maximum possible value.

### Sample Input 2

1 2 3 4


### Sample Output 2

0


### Sample Input 3

2000000000 0 0 2000000000


### Sample Output 3

2000000000