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(){
	int a,b,c,k;
	int i;
	int cnt = 0;
	
	scanf("%d%d%d%d", &a, &b, &c, &k);
	
	for(i = 0;i < a && i < k;i++){
		cnt++;
	}
	k -= a;
	k -= b;
	
	if(k){
		for(i = 0;i < c && i < k;i++){
			cnt--;
		}
	}
	printf("%d", cnt);
	
	return 0;
}