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: Wrong Answer)

#include<stdio.h>
#include<math.h>
#include<string.h>

int main(void) {
	int a, b, c, k, i;
	int ans = 0;
	scanf("%d%d%d%d", &a, &b, &c, &k);
	for (i = 1; i <= k; i++) {
		if (a > 0) {
			ans = ans + 1;
			a = a + 1;
		}
		else if (a == 0) {
			if (b > 0) {
				b = b - 1;
			}
			else if (b == 0) {
				if (c > 0) {
					ans = ans - 1;
					c = c - 1;
				}
				if (c == 0) {
					break;
				}
			}
		}
	}
	printf("%d", ans);
	return 0;
}