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) throws Exception {

//    	File file = new File("test.txt");
//    	Scanner sc = new Scanner(file);
    	Scanner sc = new Scanner(System.in);
    	long A = sc.nextLong();
    	long B = sc.nextLong();
    	long C = sc.nextLong();
    	long K = sc.nextLong();
    	sc.close();
    	long ans = 0;
    	if(A >= K){
    		ans += K;
    		System.out.println(ans);
    		return;
    	}else{
    		ans += A;
    		K -= A;
    	}
    	K -= B;
    	if(K <= 0){
    		System.out.println(ans);
    		return;
    	}
    	if(C >= K){
    		ans -= K;
    		System.out.println(ans);
    		return;
    	}else{
    		ans -= C;
    		K -= C;
    	}
    	System.out.println(ans);
    }
}