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 C (GCC 9.2.1) (judge verdict: Accepted)

#include<stdio.h>
 
int main(){
  int A,B,C,K,i,sum=0,tmp;
  
  scanf("%d%d%d%d",&A,&B,&C,&K);
  if((K-A) >= 0){
  	sum = 1*A;
    K -= A;
    if((K-B) >= 0){
    	K -= B;
      for(i=0; i<K; i++){
      	sum--;
      }
    }
  }
  else{
  	sum = K;
  }
  printf("%d", sum);
	return 0;
}