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.io.*;
import java.util.*;
class Main {
  public static int result = 0;
  public static int a = 0;
  public static int b = 0;
  public static int c = 0;
  public static int k = 0;
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        a = sc.nextInt(); //1のカード枚数
        b = sc.nextInt(); //0のカード枚数
        c = sc.nextInt(); //-1のカード枚数
        k = sc.nextInt(); //引くカードの枚数
        k = calc(a,k, 1);
        k = calc(b,k, 0);
        k = calc(c,k, -1);
        System.out.println(result);
    }
    public static int calc(int num, int k , int card){
      if(k==0) return k;
      if(num >= k){
        result += k*card;
        k=0;
      }else {
        result += num*card;
        k-=num;
      }
      return k;
    }
}