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;
fn main() {
    let mut l1 = String::new();
    let stdin = io::stdin();
    stdin.read_line(&mut l1).unwrap();
    let trimed = l1.trim_end();
    let mut itr = trimed.split_ascii_whitespace();
    let a = itr.next().unwrap().parse::<usize>().unwrap();
    let b = itr.next().unwrap().parse::<usize>().unwrap();
    let c = itr.next().unwrap().parse::<usize>().unwrap();
    let mut k = itr.next().unwrap().parse::<usize>().unwrap();
    let mut sum = 0_usize;
    if k <= a {
        k = 0;
        sum = sum + k * 1_usize;
    } else {
        k = k - a;
        sum = sum + a * 1;
    }
    if k != 0 {
        if k <= b {
            k = 0;
        } else {
            k = k - b;
        }
    }
    if k != 0 {
        if k <= c {
            sum = sum - k;
        }
    }
    println!("{}", sum);
}