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 PyPy3 (7.3.0) (judge verdict: Wrong Answer)

x = input().split()

a = int(x[0])
b = int(x[1])
c = int(x[2])
k = int(x[3])

if(a > k): # a > k
  print(1*(a-k))
  exit()
elif(k-a == 0):
  print(1*a)
  exit()
elif(k > a and k-a < b): # k > a 
  print(a)
  exit()
elif((k-a)-b == 0):
  print(a)
  exit()
elif(k-a-b <= c):
  x = (k - a - b)
  print(a-x)
  exit()