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 Haskell (GHC 7.10.3) (judge verdict: Wrong Answer)

import Control.Applicative
import Data.List
 
main = do
  [n, a, b] <- map read . words <$> getLine
  print $ f n a b
 
f :: Int -> Int -> Int -> Int
f n a b
  | n <= 0 = 0
  | n == 1 && a /= b = 0
  | a > b = 0
  | otherwise = g n a b
 
g :: Int -> Int -> Int -> Int
g n a b = length $ h n a b
 
h :: Int -> Int -> Int -> [Int]
h 1 a b = [a .. b]
h n a b = nub $ (+) <$> [a .. b] <*> h (n-1) a b