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)

#![allow(unused_macros)]

macro_rules! line {
    () => {{
        let mut buf = String::new();
        std::io::stdin().read_line(&mut buf).unwrap();
        buf
    }};
}
macro_rules! input {
    { $( $i:ident : $t:ty ),* } => {
        let ( $( $i ),* ) = match &line!().split_whitespace().collect::<Vec<_>>()[..] {
            &[ $( $i ),* ] => ( $( $i.parse::<$t>().unwrap() ),* ),
            _ => panic!(),
        };
    };
}

fn main() {
    input!(a: i64, b: i64, _c: i64, k: i64);

    println!(
        "{}",
        if k <= a {
            k
        } else if k <= a + b {
            a
        } else {
            a - (k - (a + b))
        }
    )
}