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;

int main() {
  int A, B, C, K, x, y, z;
  cin >> A >> B >> C >> K;
  
  int ans = 0;
  x = 0; y = 0; z = 0;
  for (int i = 0; i < A && i < K; i++ ){
    ans++;
    x++;
  }
  
  for (int i = 0; i < B && i + x < K; i++ ){
    y++;
  }
  
  for (int i = 0; i < C && i + x + y < K; i++ ){
    ans--;
    z++;
  }
  cout << ans << endl;
}