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;
 
#define sf(n) scanf("%d", &n)
#define pd(n) printf("%.10lf", n)
#define pf(n) printf("%d", n)
#define p() printf("\n")
#define ps() printf(" ")
#define ll long long
#define ull unsigned long long
#define MAX 1e9
const int mod = 1000 * 1000 * 1000 + 7;
#define ex 1e18
#define dbl 2e09
#define qu(q) queue<int> q
#define pqu(q) priority_queue<int> q
#define len(s) s.length()
#define sz(x) int(x.size())
#define pb(x) push_back(x)
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define F first
#define S second
#define clr(x) x.clear()
#define LOG(x) std::cout << x << std::endl;
 
const int INF = 0x3f3f3f3f;
const ll LL_INF = 0x3f3f3f3f3f3f3f3f;
const double PI = 3.14159265359;
 
int dx[6] = {-1,-1,0,0,1,1};
int dy[6] = {-1,0,-1,1,0,1};

const int N = 8e3+5;

int a[N];

int main()
{
    int a,b,c,k;
    cin>>a>>b>>c>>k;
    int ans=0;
    ans+=min(a,k);
    k-=(a+b);
    while(k>0){
        ans-=1;
        k--;
    }
    cout<<ans<<endl;
	return 0;
}