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)

use proconio::input;

fn main() {
    input! {
        a: isize,
        b: isize,
        c: isize,
        k: isize,
    }
    let (mut result, mut remain) = (0, k);
    if remain >= a {
        remain -= a;
        result += a;
    } else {
        result += remain;
        println!("{}", result);
        std::process::exit(0);
    }

    if remain >= b {
        remain -= b;
    } else {
        println!("{}", result);
        std::process::exit(0);
    }

    if remain >= c {
        remain -= c;
        result -= c;
    } else {
        result -= remain;
        println!("{}", result);
        std::process::exit(0);
    }

    if remain == 0 {
        println!("{}", result);
    } else {
        unreachable!();
    }
}