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 (Clang 10.0.0) (judge verdict: Accepted)

#include<stdio.h>

int main(void)
{
	unsigned long long int a, b, c, sum, k;

	scanf("%lld%lld%lld%lld", &a, &b, &c, &k);

	if (a >= k) {
		printf("%lld", k);
		return 0;
	}

	if (a + b >= k) {
		printf("%lld", a);
		return 0;
	}

	else {
		printf("%lld", (a - (k - b - a)));
		return 0;
	}

	return 0;
}