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++ (GCC 9.2.1) (judge verdict: Time Limit Exceeded)

#include <iostream>

using namespace std;

int main()
{
    long A, B, C, K;

    cin >> A >> B >> C >> K;

    long ANS = 0;

    for (long i = 0; i < K; i++)
    {
        if (A != 0)
        {
            ANS += 1;
            A -= 1;
            continue;
        }

        if (B != 0)
        {
            ANS += 0;
            B -= 1;
            continue;
        }

        if (C != 0)
        {
            ANS -= 1;
            C -= 1;
            continue;
        }
    }

    cout << ANS << endl;
}