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)

const input = require('fs').readFileSync('/dev/stdin', 'utf8').split('\n');
const line = input[0].split(' ')
const A = +line[0]
const B = +line[1]
const C = +line[2]
const K = +line[3]

// console.log(`A=${A}`)
// console.log(`B=${B}`)
// console.log(`C=${C}`)
// console.log(`K=${K}`)

if (K <= A) {
    // console.log('A <= K')
    console.log(K)
} else if (K <= A + B) {
    // console.log('A + B <= K')
    console.log(A)
} else {
    const effectiveC = K - (A + B);
    console.log(A - effectiveC)
}