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>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
typedef long long ll;
const int INF = 1000000000; // 10^9
int main() {
    // ifstream in("data1.txt");
    // cin.rdbuf(in.rdbuf());
    ll A,B,C,K;
    cin >> A >> B >> C >> K;

    ll ans = 0;
    ll cnt = 0;
    ll amari = 0;

    amari = K - A;
    if(amari <= 0){
        ans += K;
        cout << ans << endl;
        return 0;
    }
    ans += A;


    amari -= B;

    if(amari <= 0){
        cout << ans << endl;
        return 0;
    }

    ans -= amari;

    cout << ans << endl;
}