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++ (Clang 10.0.0) (judge verdict: Accepted)

#include <iostream>
#include <stdio.h>
#include <algorithm>
#include <math.h>
#include <list>
#include <string>
#include <map>
#include <vector>
#include <stack>
#include <queue>
#include <iomanip> // setprecisionを使用するのに必要 cout << fixed << setprecision(15) << p でpを小数点以下15桁表示
using namespace std;
#define REPD(i, a, b) for (int i = (a); i < (b); ++i)
#define REP(i, n) REPD(i, 0, n)
typedef long long ll;
#define fin(ans) cout << (ans) << '\n'
/*

*/
int main()
{
    ll A,B,C,K;
    cin >> A >> B >> C >> K;
    ll ans;
    if(0 < K && K <= A){
        ans = K;
        fin(ans);
        return 0;
    }else if(A < K){
        ans = A;
        K -= A;
    }
    K -= B;
    if(0 < K && K <= C){
        ans -= K;
        fin(ans);
    }else{
        fin(ans);
    }
    return 0;
}