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.Linq;
using System.Collections.Generic;

namespace b
{
    class Program
    {
        static void Main(string[] args)
        {
            var _ = Console.ReadLine().Split();
            var a = long.Parse(_[0]);
            var b = long.Parse(_[1]);
            var c = long.Parse(_[2]);
            var k = long.Parse(_[3]);

            var total = 0L;
            if(a > 0){
                if(k >= a){
                    total += a;
                    k -= a;
                }else{
                    total += k;
                    k = 0;
                }
            }

            if(k > 0 && b > 0){
                k -= b;
            }

            if(k > 0 && c > 0){
                if(k >= c){
                    total -= c;
                }else{
                    total -= k;
                }
            }

            Console.WriteLine(total);
        }
    }
}