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<bits/stdc++.h>
#define ll long long
using namespace std;

void solve(){
	ll a, b, c, k;
	cin >> a>>b>>c>>k;

	if(k<=a){
		cout << k <<"\n";
	}
	else if(k<=a+b){
		cout << a<<"\n";
	}
	else cout << a-(k-(a+b))<<"\n";

}

int main(){

	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	
	solve();
	
	return 0;
}