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)

def mips():
    return map(int,input().split())
def msps():
    return map(str,input().split())

import sys
A,B,C,K = mips()
ans = 0
reste = K
if A >= K:
    print(K)
    sys.exit(0)
if A < K:
    ans += A
    reste -= A
if reste <= B:
    print(ans)
    sys.exit(0)
reste -= B
if reste <= C:
    ans -= reste
    print(ans)
else:
    ans -= C
    print(ans)