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;
using System.Text;
using System.Threading.Tasks;
using System.IO;

namespace ABC
{
    class ABC167B
    {
        const string FILE = "/tmp/data.txt";

        static void Main(string[] args)
        {
#if DEBUG
            Console.SetIn(new StreamReader(FILE));
#endif
            string line;
            string[] sa;
            line = Console.ReadLine();
            sa = line.Split(' ');

            int a = int.Parse(sa[0]);
            int b = int.Parse(sa[1]);
            int c = int.Parse(sa[2]);
            int k = int.Parse(sa[3]);

            int na = Math.Min(a, k);
            k = Math.Max(k - na, 0);
            int nb = Math.Min(b, k);
            k = Math.Max(k - nb, 0);
            int nc = Math.Min(c, k);

            Console.WriteLine(na - nc);

#if DEBUG
            Console.WriteLine();
#endif
        }
    }
}