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: Accepted)

function Main(input){
  input = input.trim().split(' ').map(x=>parseInt(x));
  var a = input[0];
  var b = input[1];
  var c = input[2];
  var k = input[3];
  var ans = 0;
  if (a>k){
    ans = k;
  }else if (a+b>k){
    ans = a;
  }else{
    ans = a - (k-a-b);
  }
  console.log(ans);
}


Main(require("fs").readFileSync("/dev/stdin", "utf8"));