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 <vector>
#include <queue>
#include <algorithm>
#include <cmath>
#include <bitset>
#include <iomanip>
#include <stack>
#include <list>
#include <map>
#include <unordered_map>
#include <chrono>
#include <numeric>
using namespace std;
using ll = long long;
const ll INF = (ll)1e18+1;
const ll DIV = 1000000007;
//#define TEST
int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
#ifdef TEST
    chrono::system_clock::time_point start, end;
    start = chrono::system_clock::now();
#endif
    long A,B,C,K;
    cin >> A >> B >> C >> K;
    if(K <= A) cout << K << endl;
    else if(K > A && K <= A+B) cout << A << endl;
    else cout << A - (K - (A + B)) << endl;
#ifdef TEST
    end = chrono::system_clock::now();
    cerr << static_cast<double>(chrono::duration_cast<chrono::microseconds>(end - start).count() / 1000.0) << "[ms]" << endl;
#endif
    return 0;
}