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 Go (1.14.1) (judge verdict: Accepted)

package main

import (
    "bufio"
    "fmt"
    "os"
    "strconv"
)

var sc = bufio.NewScanner(os.Stdin)
var w = bufio.NewWriter(os.Stdout)

func nextInt() int {
    sc.Scan()
    i, e := strconv.Atoi(sc.Text())
    if e != nil {
        panic(e)
    }
    return i
}

func main() {
    sc.Split(bufio.ScanWords)
    defer w.Flush()

    a := nextInt()
    b := nextInt()
    c := nextInt()
    k := nextInt()

    t := 0
    if k < a {
        t = k
        k = 0
    } else {
        t = a
        k -= a
    }

    if k < b {
        k = 0
    } else {
        k -= b
    }

    if k < c {
        t -= k
    } else {
        t -= c
    }
    fmt.Fprintln(w, t)
}