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 std::io::*;

fn main() {
    let mut s: String = String::new();
    std::io::stdin().read_to_string(&mut s).ok();
    let mut itr = s.trim().split_whitespace();
    let a: i64 = itr.next().unwrap().parse().unwrap();
    let b: i64 = itr.next().unwrap().parse().unwrap();
    let _: i64 = itr.next().unwrap().parse().unwrap();
    let mut k: i64 = itr.next().unwrap().parse().unwrap();

    let mut ans = 0;
    if k <= a {
        println!("{}", k);
        return;
    }
    k -= a;
    ans += a;
    if k <= b {
        println!("{}", ans);
        return;
    }
    k -= b;
    println!("{}", ans - k);
}