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;
use proconio::marker::Chars;
use std::collections::HashSet;
use std::iter::Iterator;

fn main() {
    input! {
    a: i64,
    b: i64,
    c: i64,
    k: i64,
    }

    let mut ans = 0;
    let mut zan = 0;

    if a < k {
        ans = ans + a;

        zan = k - a;
        if b < zan {
            ans = ans;
            zan = zan - b;
            if c < zan {
                ans = zan - c;
            } else {
                ans = ans - zan;
            }
        } else {
            ans = ans;
        }
    } else {
        ans = 1 * k;
    }

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