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)

#![allow(unused_imports)]
use itertools::Itertools;
use proconio::{input, marker::*};
use std::cmp::*;
use std::collections::HashMap;
use std::collections::*;
use superslice::*;
use whiteread::parse_line;


fn main() {
    let (a, b, _, k): (u64, u64, u64, u64) = parse_line().unwrap();
    // a 1のカード b 0のカード c -1のカード k枚選ぶ 最大値を求める
    let mut current = k;
    if current < a {
        println!("{}", current);
        return;
    } else {
        current = current - a;
    }
    if current < b {
        println!("{}", current);
        return;
    } else {
        current = current - b;
    }
    println!("{}", a - current);
}