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;
#define rep(i, n) for(int i = 0; i < n; i++)
#define rep1(i, n) for(int i = 1; i < n+1; i++)
#define sort(A) sort(A.begin(),A.end())
#define reverse(A) reverse(A.begin(),A.end())
#define vecmin(A) *min_element(A.begin(),A.end())
#define vecmax(A) *max_element(A.begin(),A.end())
typedef long long ll;

int main(){
  
  int a,b,c,k;
  cin >> a >> b >> c >> k;
  if(k < a) cout << k << endl;
  if(a <= k && k < a+b) cout << a << endl;
  if(a+b <= k) cout << a - (k - a - b) << endl;
}