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 JavaScript (Node.js 12.16.1) (judge verdict: Accepted)

function main(input) {
  const args = input.split(' ')
  const a = Number(args[0])
  const b = Number(args[1])
  const c = Number(args[2])
  const k = Number(args[3])
  let t = k
  t -= a
  if (t <= 0) {
    if (a <= k) {
      console.log(a)
    } else {
      console.log(k)
    }
  } else {
    t -= b
    if(t <= 0) {
      console.log(a)
    } else {
      if (t < c) {
        console.log(a - t)
      } else {
        console.log(a - c)
      }
    }
  }

}
main(require('fs').readFileSync('/dev/stdin', 'utf8'))