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 1.8.0) (judge verdict: Accepted)

import org.omg.PortableInterceptor.SYSTEM_EXCEPTION;

import java.io.*;
import java.math.BigInteger;
import java.util.*;

public class Main {



    public static void main(String[] args) throws Exception {
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        String[] s = in.readLine().split(" ");
        long A = Long.parseLong(s[0]);
        long B = Long.parseLong(s[1]);
        long C = Long.parseLong(s[2]);
        long K = Long.parseLong(s[3]);
        long ans = 0;
        boolean flag = false;
        if(A > K) {
            System.out.println(K);
        } else {
            K -= A;
            if(K == 0) {
                System.out.println(A);
            } else {
                if(B > K) {
                    System.out.println(A);
                } else {
                    K -= B;
                    if(K == 0) {
                        System.out.println(A);
                    } else {
                        if(C > K) {
                            System.out.println(A - K);
                        } else {
                            System.out.println(A - C);
                        }
                    }
                }
            }
        }
    }

}