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 proconio::input;

fn main() {
    input! {
        a: i64,
        b: i64,
        _c: i64,
        k: i64, 
    }
    let l: i64 = if k >= a {
        a
    } else {
        k
    };
    let current_cards = k - l;
    if current_cards == 0 { println!("{}", l); } else {
        let n: i64 = if current_cards >= b {
            b
        } else { current_cards };
        let current_cards = current_cards - n;
        let answer = l - current_cards;
        println!("{}", answer);
    }
}