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>
#define ll long long
#define rep(i, begin, end) for (__typeof(end) i = (begin) - ((begin) > (end)); i != (end) - ((begin) > (end)); i += 1 - 2 * ((begin) > (end))) // rep(i, 1, 5) --> {1,2,3,4} // rep(i, 5, 1) --> {4,3,2,1} // rep(it, end(v), begin(v)) --> *it

using namespace std;

int main()
{
    int a, b, c, k;
    cin >> a >> b >> c >> k;
    int res = 0;
    int resA = k-a;
    if (resA <= 0)
    {
        res = k;
        cout << res;
        return 0;
    }
    else 
    {
        res = a;
        int resB = resA - b;
        if (resB <= 0)
        {
            cout << res;
            return 0;
        }
        else 
        {
            res = res - resB;
            cout << res;
            return 0;
        }
    }
    return 0;
}