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>
typedef long long int lli;
typedef unsigned long long int ulli;
#define pb push_back
#define eb emplace_back
#define vi vector <int>
#define vlli vector <lli>
#define vulli vector <ulli>
#define vchar vector <char>
#define vstr vector <string>
#define vb vector <bool>
#define fst first
#define sec second
#define srt(a) sort(a.begin(),a.end())
#define vpii vector <pair <int,int> >
#define pii pair <int,int> 
#define vplli vector <pair <lli,lli> >
#define vpulli vector <pair <ulli,ulli> >
#define vvi vector <vector <int> >
#define vvpii vector <vector <pair <int,int>> >
#define vvb vector <vector <bool> >
#define fr(i,n) for (int i = 0; i < (n); i++)
#define frbig(i,n) for (lli i = 0; i < (n); i++)
#define fra(i,a,n) for (lli i = a; i < (n); i++)
#define run(c,s) for(auto c:s) 
#define read(n) int n; cin >> n;
#define read2(x,y) int x,y; cin >> x >> y;
#define read2ll(x,y) long long int x,y; cin >> x >> y;
#define readll(n) lli n; cin >> n;
#define watch(x) cout << (#x) << " is " << (x) << endl
#define print_array(x) fr(i,x.size()) cout << x[i] << " ";
using namespace std;
const lli MOD = 1e9 + 7;
int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
    int a,b,c,k;
    cin >> a >> b >> c >> k;
    if(a+b>=k) cout << a;
    else cout << a+(a+b-k);
    return 0;
}