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)

#define ll long long int
#define forn(i, n) for (int i = 0; i < int(n); i++)
#define maxx(a,b) std::max(a,b)
#define maxxx(a,b,c) std::max(a,std::max(b,c))
#define minn(a,b) std::min(a,b)
#define minnn(a,b,c) std::min(a,std::min(b,c))

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