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)

import logging

logging.basicConfig(level=logging.INFO, format="%(message)s")
#logging.disable(logging.CRITICAL)


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

    ans = 0
    
    if A > K:
        ans += K * 1
        K = 0
    else:
        ans += A
        K = K - A
        if B > K:
            ans += K * 0
            K = K - B
        else:
            K = K - B
            if C > K:
                ans -= K
            else:
                ans -= C

    print(ans)

                
        
if __name__ == "__main__":
    main()