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)

nums = input().split(' ')
# values = []
# for i in range(int(nums[0])):
#     values.append(1)
# for i in range(int(nums[1])):
#     values.append(0)
# for i in range(int(nums[2])):
#     values.append(-1)

one_counts = int(nums[0])
zero_counts = int(nums[1])
mone_counts = int(nums[2])
top = int(nums[3])


if one_counts >= top:
    print(top)
else:
    if one_counts + zero_counts >= top:
        print(one_counts)
    else:
        print(one_counts - (top - (one_counts + zero_counts)))