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;

int main(void){
    int64_t a,b,c,k;
    cin >> a >> b >> c >> k;
    int64_t sum = 0;
    int64_t count = 0;
    int aiu = 0;
    while(aiu==0){
        for (int j = a; a > 0; a--)
        {
            sum += 1;
            count++;
            if (count==k)
            {
                aiu++;
                break;
            }
        }
        for (int n = b; b > 0; b--)
        {
            count++;
            if (count==k)
            {
                aiu++;
                break;
            }
        }
        for (int m = c; c > 0; c--)
        {
            sum -= 1;
            count++;
            if (count==k)
            {
                aiu++;
                break;
            }
        }
    }

    cout << sum << endl;
    
}