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 Lua (Lua 5.3.5) (judge verdict: Accepted)

a,b,c,k=io.read("*n","*n","*n","*n")
if a>=k then
    print(k)
elseif a<k then
    if a+b>=k then
        print(a)
    elseif a+b<k then
        if a+b+c==k then
            print(a-c)
        elseif a+b+c>k then
            print(a-(k-a-b))
        end
    end
end