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)

a,b,c,k=list(map(int,input().split()))
sum=0
if a>k:
    sum=k-a
    print(sum)
elif a==k:
    print(a)
else:
    if a+b>k:
        print(a)
    elif a+b==k:
        print(a)
    else:
        if a+b+c>k:
            sum=k-a-b
            print(a-sum)
        elif a+b+c==k:
            print(a-c)