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

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.

Examples

Input

2 1 1 3

Output

2

Input

1 2 3 4

Output

0

Input

2000000000 0 0 2000000000

Output

2000000000

见题面

见题面