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 Go (1.14.1) (judge verdict: Accepted)

package main
import "fmt"
func main(){
    // Your code here!
    
    var a,b,c,k int
    fmt.Scan(&a, &b, &c, &k)
    if a >= k{
        fmt.Println(1*k)
    }else {
        k -= a
        if b >= k{
            fmt.Println(1*a)
        }else{
            k -= b
            if k <= c{
                fmt.Println(1*a + -1*k)
            }
        }
    }
}