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)

#define rep(i,n) for (int i = 0; i < (n); ++i)
#define rept(i,s,n) for (int i = (s); i < (n); ++i)

#include <iostream>
#include <cmath>
#include <bitset>
#include <algorithm>
using namespace std;

int main() {

  long a,b,c,k, result=0;
  cin >> a>>b>>c>>k;

  if(k>0){
    if(k>=a){
      result += a;
      k-=a;
    } else{
      result += k;
      k = 0;
    }
  }

    if(k>0){
      if(k>=b){
        k-=b;
      } else{
        k = 0;
      }
    }

    if(k>0){
      if(k>=c){
        result -= c;
        k-=c;
      } else{
        result -= k;
        k = 0;
      }
    }



    cout << result << endl;
  return 0;
}