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 Haskell (GHC 8.8.3) (judge verdict: Accepted)

module Main where

import qualified Data.ByteString.Char8 as BS
import Data.Maybe
import Control.Monad
import Data.List

main :: IO ()
main = do
    [a,b,c,k] <- map (fst.fromJust.BS.readInt).BS.words <$> BS.getLine
    let one = if k < a then k else a 
    let zero = if (k-one) < b then k-one else b
    let minus = k - one - zero
    putStr $ show (one-minus)