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)

#[warn(unused_imports)]
use proconio::{
   fastout, input,
   marker::{Bytes, Chars, Isize1, Usize1}
};

#[fastout]
fn main() {
   input! {
      a:usize,
      b:usize,
      c:usize,
      mut k:usize,
   }
   let mut ans = 0;
   if a >= k {
      ans = k;
   } else {
      k -= a;
      ans += a;
      if b < k {
         ans -= k - b;
      }
   }
   println!("{}", ans);
}