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: Accepted)

fn main() {
    let (a, b, c, k) = input();
    println!("{}", solve(a, b, c, k));
}

fn input() -> (i32, i32, i32, i32) {
    let mut buf = String::new();
    std::io::stdin().read_line(&mut buf).unwrap();
    let mut iter = buf.split_whitespace();
    let a: i32 = iter.next().unwrap().parse().unwrap();
    let b: i32 = iter.next().unwrap().parse().unwrap();
    let c: i32 = iter.next().unwrap().parse().unwrap();
    let k: i32 = iter.next().unwrap().parse().unwrap();
    (a, b, c, k)
}

fn solve(a: i32, b: i32, c: i32, k: i32) -> i32 {
    let mut res = 0;
    if a - k >= 0 {
        return k;
    } else {
        res = a;
    }
    let mut remain = k - a;
    if b - remain >= 0 {
        return res;
    }
    remain  = remain - b;
    res - remain
}