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)

struct Rin{}
impl Rin{
    fn input(&self)->String{
        let mut x=String::new();
        std::io::stdin().read_line(&mut x).ok();
        x
    }
    fn inputs(&self)->String{
        let s=self.input().trim().to_string();
        s
    }
    fn inputn(&self)->i32{
        let n:i32=self.input().trim().parse().unwrap();
        n
    }
    fn inputvs(&self)->Vec<String>{
        let vs=self.input().trim().split(' ').map(|x|x.to_string()).collect();
        vs
    }
    fn inputvn(&self)->Vec<i32>{
        let vn=self.input().trim().split(' ').map(|x|x.to_string().parse().unwrap()).collect();
        vn
    }
}

fn main(){
    let rin=Rin{};
    let v=rin.inputvn();
    let a=v[0]; let b=v[1]; let c=v[2]; let mut k=v[3];
    let mut ans=0;
    if a>=k{
        println!("{}",k);
    }else if a+b>=k{
        println!("{}",a);
    }else{
        println!("{}",a-(k-a-b));
    }
}