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 C# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;

class AtCoderCS {
    static void Main(string[] args) {
        long[] ABCK = Console.ReadLine().Split(' ').Select(i => long.Parse(i)).ToArray();
        long A = ABCK[0], B = ABCK[1], C = ABCK[2], K = ABCK[3];

        long ans = 0;
        if (K >= A) {
            ans += A;
            K -= A;
        } else {
            ans += K;
            K = 0;
        }

        if (K >= B)
            K -= B;
        else
            K = 0;

        ans -= K;

        Console.WriteLine(ans);
    }
}