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 std::io::{self, Read};
use std::cmp;

macro_rules! input {
    ($it: expr) => ($it.next().unwrap().parse().unwrap());
    ($it: expr, $T: ty) => ($it.next().unwrap().parse::<$T>().unwrap());
}

fn main() {
    let mut buf = String::new();
    let mut it = {
        io::stdin().read_to_string(&mut buf).unwrap();
        buf.split_whitespace()
    };

    let a: u64 = input!(it);
    let b: u64 = input!(it);
    let c: u64 = input!(it);
    let k: u64 = input!(it);

    let mut ans: u64 = 0;
    let mut r: u64 = k;

    ans += cmp::min(a, r);
    r -= cmp::min(a, r);

    r -= cmp::min(b, r);

    ans -= cmp::min(c, r);

    println!("{}", ans);
}