Problem:
Score : 200 points

Problem Statement

Snuke has N integers. Among them, the smallest is A, and the largest is B.
We are interested in the sum of those N integers. How many different possible sums there are?

Constraints

1 ≤ N,A,B ≤ 10^9

A and B are integers.

Input

Input is given from Standard Input in the following format:

N A B

Output

Print the number of the different possible sums.

Sample Input 1

4 4 6

Sample Output 1

5

There are five possible sums: 18=4+4+4+6, 19=4+4+5+6, 20=4+5+5+6, 21=4+5+6+6 and 22=4+6+6+6.

Sample Input 2

5 4 3

Sample Output 2

0

Sample Input 3

1 7 10

Sample Output 3

0

Sample Input 4

1 3 3

Sample Output 4

1

Solution in OCaml (4.02.3) (judge verdict: Runtime Error)

let () =
  let s = read_line () in
  Array.init (String.length s) (fun i -> s.[i])
  |> Array.mapi (fun i -> function
    | 'U' -> 2 * i + String.length s - 1 - i
    | 'D' -> i + (String.length s - 1 - i) * 2)
  |> Array.fold_left ( + ) 0
  |> Printf.printf "%d\n"