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: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication6
{
    class Program
    {
        static void Main(string[] args)
        {
            //var length = c2i(RL());
            var rl = spr(RL()).Select(x=>c2i(x)).ToList();
            var A=rl[0];
            var B=rl[1];
            var C = rl[2];
            var K = rl[3];
            long ret = 0;
            if (K <= A)
            {
                ret = A;
            }
            else if (K <= (A + B))
            {
                ret = A;
            }
            else
            {
                ret = A+((A+B) - K);
            }



            Console.WriteLine((ret));
            //Console.ReadLine();
        
        }
        static string RL() { return Console.ReadLine().Trim(); }
        static IEnumerable<string> spr(string s) { return s.Split(' '); }
        static Int64 c2i(string c) { return Int64.Parse(c); }
        //static double c2d(string c) { return double.Parse(c); }
        static string bool2ret(bool b) { return b ? "Yes" : "No"; }
    }
}