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: Time Limit Exceeded)

A,B,C,K = map(int,input().split())
result = 0
#A分引く
if (K - A) < 0:
    for i in range(A):
        if K <= 0:
            break
        result = result + 1
        K  -= 1
else:
    K -= A
    result += 1*A

if (K-B) < 0:
    for i in range(B):
        if K <= 0:
            break
        K -= 1
else:
    K -= B

if (K-C) < 0:
    for i in range(C):
        if K <= 0:
            break
        K -= 1
        result -= 1
else:
    K -= C
    result -= C
print(result)