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<bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
int main()
{  
   ll a,b,c,d,sum=0;
   cin>>a>>b>>c>>d;
   while(1){
  if(a>=d) {
       cout<<d<<endl;
       return 0;
       break;
   }
    if(a<d) {
       sum+=a;
       d-=a;
       a=0;
   }
   if(d>0){
      if(b<d) d-=b;
      else {
          cout<<sum<<endl;
          return 0;
          break;
      }
   }
   if(d>0){
       sum-=c;
       cout<<sum<<endl;
       return 0;
       break;
   }
   }
}