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;

fn main() {
    input! {
        a: usize,
        b: usize,
        c: usize,
        k: usize,
    }

    let mut answer = 0;
    let mut count = k;

    for _ in 0..a {
        if count <= 0 {
            println!("{:?}", answer);
            return;
        }

        if a <= count {
            count -= a;
            answer += a;
            break;
        } else {
            answer += count;
            println!("{:?}", answer);
            return;
        }
    }

    for _ in 0..b {
        if count <= 0 {
            println!("{:?}", answer);
            return;
        }

        if b <= count {
            count -= b;
            break;
        } else {
            println!("{:?}", answer);
            return;
        }
    }

    for _ in 0..c {
        if count <= 0 {
            println!("{:?}", answer);
            return;
        }

        if c <= count {
            count -= c;
            answer -= c;
            break;
        } else {
            answer -= count;
            println!("{:?}", answer);
            return;
        }
    }

    println!("{:?}", answer);
}