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 <bits/stdc++.h>
using namespace std;
 
int main() {
  int64_t A, B, C, K;
  cin >> A >> B >> C >> K;
  int sum = 0;
  vector<int> vec;
  for(int i = 0; i <= A; i++){
    for(int j = 0; j <= B; j++ ){
      for(int k = 0; k <= C; k++){
        if( i + j + k == K){
          sum = 1 * i + 0 * j + (-1) * k;
          vec.push_back(sum);
        }
      }
    }
  }
  sort(vec.begin(), vec.end()); 
  reverse(vec.begin(), vec.end());
  cout << vec.at(0) << endl;
}