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: Wrong Answer)

S = list(map(int,input().split()))

if S[0] + S[1] + S[2] >= 2 * 10 ** 9:
    print('Error')
elif S[0] >= S[3]:
    print(S[3])
elif S[3] > S[0] and S[3] <= S[0] + S[1]:
    print(S[0])
elif S[3] > S[0] + S[1] and S[3] <= S[0] + S[1] + S[2]:
    print(-1 * (S[3] - S[0] - S[1]) + S[0])
else:
    print('Error')