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: Time Limit Exceeded)

#include <iostream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <cstdlib>
#include <string>
#define arep(a,i,n) for(int i=(a);i<(n);i++)
#define rep(i,n) for(int i=0;i<(n);i++)
#define cinf(x,n) for(int i=0;i<(n);i++)cin>>x[i];
#define coutf(x,n) for(int i=0;i<(n);i++)cout<<x[i]<<endl;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;

using namespace std;

int main(){
	ll a,b,c,k,sum=0;
	cin >> a >> b >> c >> k;
	while(k!=0){
		if(a!=0){
			sum+=1;
			a--;
		}
		else if(b!=0){
			sum+=0;
			b--;
		}
		else if(c!=0){
			sum-=1;
			c--;
		}
		k--;
	}
	cout << sum << endl;
}