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

#define int64 long long

int main()
{
	int64 aa, bb, cc, kk;
	scanf("%lld %lld %lld %lld", &aa, &bb, &cc, &kk);
	if(kk <= aa)
	{
		printf("%lld\n", kk);
		return 0;
	}
	else if(kk <= aa + bb)
	{
		printf("%lld\n", aa);
		return 0;
	}
	else
	{
		printf("%lld\n", (aa - (kk - aa - bb)));
		return 0;
	}
	return 0;
}