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(void)
{
	int i,a_value=1,b_value=0,c_value=-1,a_number,b_number,c_number,k,max_value,max_number;

	scanf("%d%d%d%d",&a_number,&b_number,&c_number,&k);

	max_number = a_number + b_number + c_number;

	for(i=0;i< max_number-k; i++){
		if(c_number == 0){
			if(b_number == 0){
				if(a_number == 0){
				}
				else
					a_number--;
			}
			else
				b_number--;
		}
		else
			c_number--;
	}

	max_value = a_value * a_number + b_value * b_number + c_value * c_number;

	printf("%d\n",max_value);

	return 0;
}