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: Wrong Answer)

#include <bits/stdc++.h>
#include <algorithm>  
#include <unordered_set>
#define _USE_MATH_DEFINES
#include <cmath>
#define ll long long

using namespace std;

const double pi = 3.14159265358979323846;

vector<int> g[100005];

int main() {

	ios_base::sync_with_stdio(false);
	cin.tie(NULL);

	ll A, B, C, K;

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

	if (A > K) {
		cout << K << endl;
	}
	else {

		ll left = K - A;

		if (B > left) {
			cout << left << endl;
		}
		else {

			ll evenMoreLeft = left - B;
			cout << evenMoreLeft * -1 + 0 + A << endl;
		}
	}

	return 0;
}