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: Accepted)

# frozen_string_literal: true

input = gets.chomp.split
a = input[0].to_i
b = input[1].to_i
c = input[2].to_i
k = input[3].to_i

point = 0
ka = k - a
if ka <= 0
    point = k
else
    point = a
    kb = ka - b
    if kb > 0
        # kc = kb - c
        # if kc <= 0
        #     point = a - c
        # else
            point = a - kb
        # end
    end
end

puts point