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)

// INCLUDES
#include <bits/stdc++.h>
#include<assert.h>
#include <ext/pb_ds/assoc_container.hpp> 
#include <ext/pb_ds/tree_policy.hpp>
//DEFINES
#define MAX 1000001
#define pii pair<int, int>
#define F first
#define S second
#define all(s) begin(s),end(s)
#define MIN3POS(a, b, c) (a) =< (b) ? ((a) =< (c) ? 1 : 3) : ((b) =< (c) ? 2 : 3)
#define MAX3POS(a,b,c) (a) >= (b) ? ((a) >= (c) ? 1 : 3) : ((b) >= (c) ? 2:3)
#define endl '\n'
#define int long long
#define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>
#define FOR(i, begin, end) for (__typeof(end) i = (begin) - ((begin) > (end)); i != (end) - ((begin) > (end)); i += 1 - 2 * ((begin) > (end)))
#define IOS   ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define error(args...) { string _s = #args; replace(_s.begin(), _s.end(), ',', ' '); stringstream _ss(_s); istream_iterator<string> _it(_ss); err(_it, args);}
//NAMESPACES
using namespace __gnu_pbds; 
using namespace std;
vector<string> vec_splitter(string s) {
    s += ',';
    vector<string> res;
    while(!s.empty()) {
        res.push_back(s.substr(0, s.find(',')));
        s = s.substr(s.find(',') + 1);
    }
    return res;
}
void debug_out(
vector<string> __attribute__ ((unused)) args,
__attribute__ ((unused)) int idx, 
__attribute__ ((unused)) int LINE_NUM) { cerr << endl; } 
template <typename Head, typename... Tail>
void debug_out(vector<string> args, int idx, int LINE_NUM, Head H, Tail... T) {
    if(idx > 0) cerr << ", "; else cerr << "Line(" << LINE_NUM << ") ";
    stringstream ss; ss << H;
    cerr << args[idx] << " = " << ss.str();
    debug_out(args, idx + 1, LINE_NUM, T...);
}
#ifdef XOX
#define debug(...) debug_out(vec_splitter(#__VA_ARGS__), 0, __LINE__, __VA_ARGS__)
#else
#define debug(...) 42
#endif
//HELPERS

vector<int> powers2(32,0);void initialize(){ for(int i=1;i<powers2.size();i++) powers2[i] = powers2[i-1]*2;}
int32_t main()
{
IOS
int a,b,c,k;
cin>>a>>b>>c>>k;
int sum = 0;
if(k>=a) sum+=a,k-=a;
else sum+=k,k=0;
if(k>=b) k-=b;
else if(k>0) k=0;
if(k>=c) sum-=(c),k-=c;
else if(k>0) sum-=k,k=0;
cout<<sum;
return 0;
}
// Use emplace back in place of pushback
// Use tie function , for object destructuring