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.Diagnostics.CodeAnalysis;
using System.Runtime.InteropServices;
using System.Runtime.Serialization;
using System.Security.Cryptography.X509Certificates;

namespace hello_world
{class Program
	{
		static void Main(string[] args)
		{
			string[] input = Console.ReadLine().Split(" ");
			int A = int.Parse(input[0]);
			int B = int.Parse(input[1]);
			int C = int.Parse(input[2]);
			int K = int.Parse(input[3]);
			int sum = 0;

			for(int i = 0; i < K; i++)
			{
				int kk = K - A - B;
				if (A >= K)
					sum += K;
				
				else if (A + B + C >= K)
				{
					sum = 2 * A - K + B;
				}
				else if (A + B + C < K)
					sum = A - B;
				
				
				
			}
			Console.WriteLine(sum);
		}
	}

}