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 FOR(i, n) for (int i = 0; i < n; i++)
#define v(a, n) vector<int> a(n, 0)
#define s(a, n) vector<string> a(n, "")
#define lb(v, x) lower_bound(v.begin(), v.end(), x)
#define ub(v, x) upper_bound(v.begin(), v.end(), x)
#define ull unsigned long long
#define pb push_back
#define mp make_pair
#define ll long long
#define mod 1000000007
void dfs(vector<vector<int>> &d, vector<vector<int>> &g, int node, int p, vector<int> &vis);
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    ll n,m,s,k;
    cin>>n>>m>>s>>k;
    if( k > n + m)
    {
       cout<< n+m-k<<"\n";
    }
    else
      cout<<min(n,k)<<"\n";
}