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: Accepted)

#include <bits/stdc++.h>
using namespace std;

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

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

	int ans = 0;
	int remainder = K;

	if (remainder > A) {
		ans += A;
		remainder -= A;
	}
	else if (remainder == A) {
		ans += A;
		remainder = 0;
	}
	else if (remainder < A) {
		ans += remainder;
		remainder = 0;
	}

	if (remainder > B) {
		remainder -= B;
	}
	else if (remainder == B) {
		remainder = 0;
	}
	else if (remainder < B) {
		remainder = 0;
	}

	if (remainder > C) {
		ans -= C;
		remainder -= C;
	}
	else if (remainder == C) {
		ans -= C;
		remainder = 0;
	}
	else if (remainder < C) {
		ans -= remainder;
		remainder = 0;
	}

	cout << ans << endl;

	return 0;
}