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;
#define pb push_back
#define mp make_pair
#define F first
#define S second
#define sz(x) (int)x.size()
#define all(x) (x).begin(), (x).end()
#define Red ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define rep(i, n) for(int i =0 ; i < n; ++i)
#define Rep(i,a,b) for(int i=a;i<=b;i++)
#define pii pair < int, int >
typedef vector<int> vi;
typedef  long long ll;
const int mod =1e9+7;
const int N = (int)2e5 + 5;



void solve(){
	ll a,b,c,k;
	cin>>a>>b>>c>>k;
	if(a+b>=k){
		cout<<a;
		return;
	}
	ll mx=a*1ll;
	ll d=k*1ll-(a+b)*1ll;
	cout<<a*1ll-d*1ll;
}

int main(){
	Red;
	int t=1;
	//cin>>t;
	while(t--)
	solve();
	return 0;
}