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;
using ll = long long;
using p = pair<int, int>;
#define INF 1001001001
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define repX(i, n ,x) for (int i = x; i < (int)(n); ++i)
#define repBack(i, n) for (int i = n; i >= 0; --i)
#define dup(x,y) (((x)+(y)-1)/(y))

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

    return 0;
}