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)

/*
author : rahil_1407
motto : Time Management,Consistency,Patience!!
*/

#include <bits/stdc++.h>
#define SPEED ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0)
#define endl '\n'
#define f first
#define s second
#define pii pair<int,int>
#define vi vector<int>
#define mp make_pair
#define pb push_back
#define For(i,a,b) for(int i=a;i<b;i++)
#define ford(i,a,b) for(int i=a;i>=b;i--)
#define pi 3.1415926536
#define MAX 1000005
#define ll int long long

const ll N=10e8+7;
using namespace std;

int main()
{
    SPEED;
	int a,b,c,k;
	cin>>a>>b>>c>>k;

	if(k<=a)
	 cout<<k<<endl;
	else
	{
		int ans=a;
		k-=a;
		if(k<=b)
		 cout<<ans<<endl;
		else
		{
			k-=b;
			while(k--)
			 ans--;

			cout<<ans<<endl;
		}
	}
}