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 S = String::new();
    io::stdin().read_line(&mut S);
    let vec :Vec<&str> = S.trim().split_whitespace().collect();
    let A :i32 = vec[0].parse().unwrap();
    let B :i32 = vec[1].parse().unwrap();
    let C :i32 = vec[2].parse().unwrap();
    let mut K :i32 = vec[3].parse().unwrap();
    let mut total :i32 = 0;
    if K >= A {
        total = A;
        K -= A;
    }else{
        total = K;
        println!("{}",total);
        return ();
    }
    if K >= B {
        K -= B;
    }else{
        println!("{}",total);
        return ();
    }
    if K >= C {
        total -= C;
    }else{
        total == K;
    }
    println!("{}",total);
}