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: Wrong Answer)

#include <iostream>
#include <algorithm>
using namespace std;

int a, b, c, k, i, x;
int main(){
cin>>a>>b>>c>>k;
if(k==0){
  cout<<0;
  return 0;
}
if(k>=a+b){
  x=a;
  k=k-a-b;  
}
else if(k>=a){
  cout<<a;
  return 0;
}
else{ 
  cout<<a-k;
  return 0;
}
if(k==0){
  cout<<x;
  return 0;
}
else
  cout<<x-k;
}