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: Wrong Answer)

def main(a, b, c, k):
    total = 0
    counts = 0
    while counts == k:
        counts += 1
        if a > 0:
            total += 1
            a -= 1
        elif b > 0:
            b -= 1
        else:
            total -= 1
            c -= 1
    return total


if __name__ == '__main__':
    a, b, c, k = tuple(map(int, input().split(' ')))
    print(main(a, b, c, k))