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 (
	"fmt"
)

func main() {
	request := make([]int, 4)
	for i := 0; i < 4; i++ {
		fmt.Scanf("%d", &request[i])
	}
	size := request[3]

	result := linear(request[0], request[1], size)
	fmt.Printf("%d", result)
}

func linear(numA int, numB int, size int) int {
	sum := 0
	for i := 0; i < numA; i++ {
		sum += 1
	}
	remain := size - numA - numB
	if remain < 0 {
		return sum
	}
	for i := 0; i < remain; i++ {
		if sum <= 0 {
			break
		}
		sum -= 1
	}
	return sum
}