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: Wrong Answer)

package main

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

var sc = bufio.NewScanner(os.Stdin)

func stringsFiledsToInts() []int {
	sc.Scan()
	r := []int{}
	ss := strings.Fields(sc.Text())
	for _, s := range ss {
		i, e := strconv.Atoi(s)
		if e != nil {
			panic(e)
		}
		r = append(r, i)
	}
	return r
}

func main() {
	inputs := stringsFiledsToInts()
	A := inputs[0]
	B := inputs[1]
	C := inputs[2]
	K := inputs[3]

	if K <= A {
		fmt.Print(1 * A)
	} else if K <= A+B {
		fmt.Print(1 * A)
	} else {
		fmt.Print(1*A + -1*int(math.Abs(float64(C-B))))
	}
}