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 Java (OpenJDK 11.0.6) (judge verdict: Accepted)

import java.util.Scanner;

public class Main {
    public static void main(String args[]){
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int c = sc.nextInt();
        int k = sc.nextInt();

        int ans = 0;
        if(a <= k){
            ans += a;
            if(k-a >= b){//aを使い切った後まだ使えるならb
                //bを使えるだけ使う
                if(k-a-b >= c){//bも使い切って、残りの枚数がcより少なければ
                    ans -= c;
                }else{//cの方が多ければ
                    ans -= k-a-b;//全部使い切る
                }
            }else{
                //bで使い切って終わり
            }
        }else{//aだけで終わるなら
            ans += k;
        }
        System.out.println(ans);
    }
}