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)

z = input().split()
a=int(z[0])
b=int(z[1])
c=int(z[2])
k=int(z[3])
res=0

if k>=a:
 res=res+a
 if k-1>=b:
   res=res+b-b
   if k-(a+b)>=c:
    res=res+c-2*c
   else:
    res=res+(k-a-b)-2*(k-a-b)
 else:
   res=res+(k-a)-(k-a)
else:
 res=res+k
print(res)