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 Rust (1.42.0) (judge verdict: Wrong Answer)

use proconio::input;
use proconio::marker::Chars;

fn main() {
	input! {
		mut a: i32,
		mut b: i32,
		mut c: i32,
		mut k: i32,
	}
	// a→b→cと順番に取っていくのが最大値になる
	// パターンは4とおりある
	// ① kが a + b + cの合計より大きい
	// ② kが a + b の合計より大きい
	// ③ kが a より大きい
	// ④ kが a　より小さい
	if k >= (a + b + c) {
		if a - c < 0 {
			println!("0");
			return;
		}
		println!("{}", a - c);
	} else if k >= (a + b) {
		println!("{}", a);
	} else if k >= a {
		println!("{}", k - a);
	} else {
		println!("{}", k);
	}
}