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 ll;

const int maxn=1e5+5;
vector<int>adj[maxn];
int visited[maxn];

//void bfs(int v){
//    visited[v]=1;
//    queue<int>q;
//    q.push(v);
//    while(!q.empty()){
//        int p=q.front();
//        q.pop();
//        for(auto u:adj[p]){
//            if(!visited[u]){
//                visited[u]=p;
//                q.push(u);
//            }
//        }
//    }
//}
void solve()
{
    ll a,b,c,k;
    cin>>a>>b>>c>>k;
    if((a+b)>=k){
        if(k<a){
            cout<<k<<endl;
        }
        else{
        cout<<a<<endl;}
    }
    else {
        ll temp=k-(a+b);
        cout<<a-temp<<endl;
    }
}

    int main()
    {
        ios::sync_with_stdio(0);
        cin.tie(0);
        solve();
        return 0;
    }