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_imports)]

//input
use proconio::input;
use proconio::marker::{Bytes, Chars};
//use std::io::Read;

//collections
//use std::collections::BTreeMap;
//use std::collections::BTreeSet;
//use std::collections::HashMap;
//use std::collections::HashSet;
//use std::collections::VecDeque;
//use std::collections::BinaryHeap;

//use std::cmp::*;

fn main() {
    input! {
        a: i64,
        b: i64,
        c: i64,
        mut k: i64,
    }
    let mut ans = 0i64;

    if k >= a {
        ans += a;
        k -= a;
    } else {
        ans += k;
        k = 0;
    }

    if k >= b {
        k -= b;
    } else {
        k = 0;
    }
    if k >= c {
        ans -= c;
        k -= c;
    } else {
        ans -= k;
        k = 0;
    }

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