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<bits/stdc++.h>
using namespace std;
int main(void){
	long long int a[3]; 
	long long int k, ans = 0;
	scanf("%lld%lld%lld%lld", &a[0], &a[1], &a[2], &k);
	for(int i = 0; k > 0, i < 3; i++){
//		printf("%d %d\n", k, ans);
		if(i == 0){
			ans += a[i];
			k -= a[i];
		}else if(i == 1){
			k -= a[i];
		}else{
			ans -= k;
			k = 0;
		}
	}
	printf("%lld\n", ans);
}