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;

namespace test
{
    class MainClass
    {
        public static void Main(string[] args)
        {

            //問題167
            string[] line = Console.ReadLine().Split(' ');

            int A = int.Parse(line[0]);
            int B = int.Parse(line[1]);
            int C = int.Parse(line[2]);
            int K = int.Parse(line[3]);


            int ans = 0;
            //for (int i = 0; i < K; i++)
            //{
            //    if (A > 0)
            //    {
            //        ans += 1;
            //        A--;
            //    }
            //    else if (B > 0)
            //    {
            //        B--;
            //    }
            //    else
            //    {
            //        ans--;
            //        C--;
            //    }
            //}

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

            }

            Console.WriteLine(ans);
        }


    }
}