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 a,b,c,k,sa1,sa2,sum;
	scanf("%d %d %d %d",&a,&b,&c,&k);
	sa1=k-a;
	if(sa1<0){
		sa1=0;
	}
	sum=0;
	sum+=k-sa1;
	if(sa1>=1){
	   sa2=sa1-b;
	   if(sa2>=1){
		   sum-=sa2;
	   }
	}
	printf("%d\n",sum);
	return 0;
}