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: Wrong Answer)

#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define llu unsigned long long 
#define ll long long 
ll read() { ll  x; if (scanf("%lld", &x) == -1)exit(0); return x; }
#define vi vector<int>
#define vb vector<bool>
#define LOCAL_JUDGE
void c_p_c()
{
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#ifdef LOCAL_JUDGE
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
}

int main() {
    //c_p_c();
    ll a = read(); ll b = read();ll c = read();ll k = read();
    if (k > a) {
        if ((k - (b + a)) <= c)
            cout << a - (k - (b + a)) << endl;
        else
            cout << a << endl;
    }
    else cout << a << endl;
}