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;
 
typedef long long int ll;
 
typedef pair<int, int> pii;
typedef pair<ll,ll> pll;
 
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<pii> vpii;
typedef vector<pll> vpll;
 
#define ff first
#define ss second
#define pb emplace_back
#define all(x) (x).begin(), (x).end()
#define mem(a) memset(a , 0 ,sizeof a)
#define rep(i,a,b) for(int i=a ; i<b ; ++i)
#define deb(x) cout << #x << " - " << x << "\n";
#define deb2(x,y) cerr<<#x<<" :: "<<x<<"\t"<<#y<<" :: "<<y<<"\n"
#define IOS ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
#define D2(x) { cerr << "[" << #x << ": "; for(auto it:x) cerr << it << " "; cerr << "]\n"; }
#define clz(x) __builtin_clzll(x)
#define bit(x) __builtin_popcount(x)
//(a / b) + ((a % b) != 0);
 
#define PI 3.141592653589793
const ll MOD = 1e9 + 7;
const ll INF = 10000000000000000;
const ll MAX_N = 1e5 + 7;

int main() {
    IOS;
    ll a,b,c,k; cin>>a>>b>>c>>k;
    if(a+b>=k){
        cout<<min(a,k);
    }
    else{
        ll res = k - (a+b);
        cout<< a - res;
    }
    return 0;
}