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: Runtime Error)

use proconio::input;
const A: i32 = 1;
const B: i32 = 0;
const C: i32 = -1;

fn main() {
    input! {
        a: usize,
        b: usize,
        c: usize,
        k: usize,
    };
    if c == 0 {
        println!("{}", a);
        return;
    }
    let mut all = Vec::with_capacity(k);
    let mut aa = vec![A; a];
    let mut bb = vec![B; b];
    let mut cc = vec![C; c];
    all.append(&mut aa);
    all.append(&mut bb);
    all.append(&mut cc);
    let ans: i32 = all.get(0..k).unwrap().iter().sum();
    println!("{:?}", ans);
}