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: Runtime Error)

A,B,C,D = map(int,input().split())
# a = [1] * A + [0] * B + [-1] * C
if (A+B+C) == D:
    
    a = 1 * A + 0 * B + (-1 * C)
    
elif (B >= (D-A)) and (C >= (D-A+B)):
    a = 1 * A + 0 * B + (-1 * (D-A+B))
    
elif A >= D:
    a = 1 * D
    
print(a)