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 num1 = Integer.parseInt(sc.next());
	int num0 = Integer.parseInt(sc.next());
    int numMinus1 = Integer.parseInt(sc.next());
    int numToSelect = Integer.parseInt(sc.next());

    int sum = 0;
	if(numToSelect <= num1){
    	sum = numToSelect * 1;
    }else if(num1 < numToSelect && numToSelect <= (num1+num0)){
        sum = num1 * 1;
    }else if((num1+num0) < numToSelect && numToSelect <= (num1+num0+numMinus1)){
        sum = num1 * 1 + (numToSelect-(num1+num0)) * -1;
    }else if((num1+num0+numMinus1) < numToSelect){
      	sum = num1 * 1 + numMinus1 * -1;
    }

    System.out.println(sum);
  }
}