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: Accepted)

main :: IO ()
main = do
  param <- reads2List :: IO [Int]
  let n = head param
  let a = param !! 1
  let b = last param
  print $ solve n a b

s2List :: Read a => String -> [a]
s2List = fmap read . words

reads2List :: Read a => IO [a]
reads2List = do
  s <- getLine
  return (s2List s)

solve :: Int -> Int -> Int -> Int
solve 1 a b = if a == b then 1 else 0
solve n a b | a > b = 0
            | otherwise = (sum maxi - sum mini) + 1 where
              mini = b : replicate (n - 1) a
              maxi = a : replicate (n - 1) b