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 JavaScript (Node.js 12.16.1) (judge verdict: Wrong Answer)

"use strict";

const main = arg => {
    const inputList = arg.trim().split("\n");
    // 回答を記述
    const A = BigInt(inputList[0].split(" ")[0]);
    const B = BigInt(inputList[0].split(" ")[1]);
    const C = BigInt(inputList[0].split(" ")[2]);
    const K = BigInt(inputList[0].split(" ")[3]);
  
    if (K <= (A + B)) {
      console.log(BigInt.asUintN(64, A).toString())
    } else {
      // A + B <= K <= A + B + C
      const minus = K - (A + B);
      console.log(BigInt.asUintN(64,A - minus).toString())
    } 
  
  }

main(require('fs').readFileSync('/dev/stdin', 'utf8'));