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>
#include <algorithm>
#define rep(i, n) for (int i=0; i<n; ++i)
#define all(obj) (obj).begin(),(obj).end()
using namespace std;
typedef long long ll;

int main(){
    ll A, B, C, K;
    cin >> A >> B >> C >> K;
    if(A>=K){
        cout << A << endl;
    }
    else if(A+B>=K){
        cout << A << endl;
    }
    else{
        if(A+B+C<=K){
            cout << A-C << endl;
        }
        else{
            cout << A-(K-A-B) << endl;
        }
    }
}