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)

import Control.Monad.ST
import Data.Char
 
 
readInt :: IO Int
readInt = read <$> getLine :: IO Int
 
readIntSplit :: IO [Int]
readIntSplit = map read . words <$> getLine :: IO [Int]
 
readStr :: IO String
readStr = getLine
 
readStrSplit :: IO [String]
readStrSplit = map read . words <$> getLine

solve :: Int -> Int -> Int -> (Int, Int)
solve value x k
  | value <= k = (x * value, k - value)
  | k > 0 = (x * k, 0)
  | otherwise = (0, 0)

main = do
  [a, b, c, k] <- readIntSplit
  let (ans1, k1) = solve a 1 k
  let (_, k2) = solve b 0 k1
  let (ans3, _) = solve c (-1) k2
  print $ ans1 + ans3