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: Accepted)

t=list(map(int,input().split(" ")))
a=t[0]
b=t[1]
c=t[2]
k=t[3]
flag=0
sum = 0
if(a>k):
    sum=sum+k
    flag=1
    k=0
else:
    k=k-a
    sum=sum+a
    flag=1
    # print(k,sum)
if(flag==1):
    if(k!=0):
        if(b>k):
            k=0
            flag=2
        else:
            k=k-b
            flag=2
if(flag==2):
    if(k!=0):
        if(c>k):
            sum=sum-k
        else:
            k=k-c
            sum=sum-c
print(sum)