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<iostream>
#include<string>
#include<vector>
#include<algorithm>
#include<iomanip>
#define rep(i,n) for (int i = 0; i < (n); ++i)
typedef long long ll;
using namespace std;

int main(){
    int A,B,C,K;
    cin >> A >> B >> C >> K;
    int ans;
    if(K>=A){
        ans += A;
        if(K-A > B){
            if(K-A-B > C){
                ans -= C;
            }else{
                ans -= K-A-B;
            }
        }else{}
    }else{
        ans = K;
    }
    cout << ans << endl;
    return 0;
}