Problem:
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 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.

Sample Input 1

2 1 1 3

Sample Output 1

2

Consider picking up two cards with 1s 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

Solution in PyPy3 (7.3.0) (judge verdict: Accepted)

A, B, C, K = map(int, input().split())
ans = 0
flag = 0
if A > 0:
    if K > A:
        ans += A
        K -= A
    else:
        ans += K
        flag += 1
if B > 0 and flag == 0:
    K -= B
    if K < 1:
        flag += 1
if C > 0 and flag == 0:
    if K > C:
        ans -= C
    else:
        ans -= K
print(ans)