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 Fortran (GNU Fortran 9.2.1) (judge verdict: Accepted)

program main
  integer(8) :: A,B,C,K
  integer(8) :: i,j
  read(*,*) A,B,C,K
  if ( K-A > 0) then
     if (K-A-B > 0 ) then
        write(*,'(i0)') A-(K-A-B)
     else
        write(*,'(i0)') A
     end if
  else 
     write(*,'(i0)')  K
  end if
end program main