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, zan, ret = 0;

  	scanf("%d %d %d %d", &a, &b, &c, &k);
  	if (a + b + c > k ) {
	  zan = k;
    } else {
      zan = a + b + c;
    }
	if (a < k) {
		ret = a;
    } else {
      	ret = k;
    }
  	zan -= a;
  
  	if (zan > b) {
      zan -= b;
      if (zan > 0) {
        ret -= zan;
      }
    }
  
  	printf("%d\n", ret);
  	return 0;
}