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 Ruby (2.7.1) (judge verdict: Wrong Answer)

line = gets.split(' ').map(&:to_i)

A = line[0]
b = line[1]
c = line[2]
k = line[3]

max = 0

if (k - A) >= 0
  max += A * 1
  k -= A
end

if (k - b) >= 0
  k -= b
end


if (k - c) >= 0
  max -= c * 1
elsif c > k && k > 0
  max -= k * 1
end 


  
puts max