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.