101671: [AtCoder]ABC167 B - Easy Linear Programming

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