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 PHP (7.4.4) (judge verdict: Accepted)

 <?php   
fscanf(STDIN,"%d %d %d %d",$a,$b,$c,$k);
//fscanf(STDIN,"%s",$t);

//$li = explode(" ",trim(fgets(STDIN)));
$sum=0;
if($a<$k){
  $sum+=$a*1;
  $k = $k-$a;//残り枚数
}else{
  $sum+=$k*1;
  echo $sum."\n";
  exit;
}

if($b<$k){
  $sum+=$b*0;
  $k = $k-$b;//残り枚数
}else{
  $sum+=$k*0;
  echo $sum."\n";
  exit;
}

if($c<$k){
  $sum+=$c*-1;
}else{
  $sum+=$k*-1;
  echo $sum."\n";
  exit;
}


        
echo "${sum}\n";