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 Python (3.8.2) (judge verdict: Accepted)

A, B, C, K = map(int, input().split())


def f(A, B, C, K) :
    
    sum = 0

    if K - A >= 0 :
        K = K - A
        sum = sum + (1 * A)
    else :
        sum = sum + (1 * K)
        K = 0

    if K <= 0 :
       return sum

    if K - B >= 0 :
        K = K - B
        sum = sum + (0 * B)
    else :
        sum = sum + (0 * K)
        K = 0

    if K <= 0 :
       return sum

    if K - C >= 0 :
        K = K - C
        sum = sum + (-1 * C)
    else :
        sum = sum + (-1 * K)
        K = 0

    if K <= 0 :
       return sum


print(f(A, B, C, K))