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 gcd(a,b) __gcd(a,b)
#define pb push_back
#define sevensins ios_base::sync_with_stdio(false);cin.tie(NULL);
#define ll long long int
#define mod  1000000007
#define vect vector<long long int>
#define bins binary_search
#define vecti vector<int>::iterator
#define bitout __builtin_popcount
int main() 
{sevensins
    ll i,j,k,l,n;
    ll a,b,c;
    
    cin>>a>>b>>c>>k;
    
    ll sum=0;
    
    if(k<=a)
    sum=k;
    else
    {
        sum=a;
        k-=a;
        if(k<=b&&k>=0)
        {
            k=0;
        }
        else
        {
            k-=b;
            sum-=k;
        }
    }
    cout<<sum<<"\n";
    
    
return 0;
}