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 (
        "fmt"
)

func solution(a, b, c, k int) int {
        ans := 0

        if a >= k {
                return k
        } else {
                ans = a
                k -= a
        }

        if b >= k {
                return ans
        } else {
                k -= b
        }
        return ans - k
}

func main() {
        var a, b, c, k int
        fmt.Scan(&a, &b, &c, &k)
        fmt.Println(solution(a, b, c, k))
}