Problem:
Score : 400 points

Problem Statement

Mountaineers Mr. Takahashi and Mr. Aoki recently trekked across a certain famous mountain range.
The mountain range consists of N mountains, extending from west to east in a straight line as Mt. 1, Mt. 2, ..., Mt. N.
Mr. Takahashi traversed the range from the west and Mr. Aoki from the east.

The height of Mt. i is h_i, but they have forgotten the value of each h_i.
Instead, for each i (1 ≤ i ≤ N), they recorded the maximum height of the mountains climbed up to the time they reached the peak of Mt. i (including Mt. i).
Mr. Takahashi's record is T_i and Mr. Aoki's record is A_i.

We know that the height of each mountain h_i is a positive integer.
Compute the number of the possible sequences of the mountains' heights, modulo 10^9 + 7.

Note that the records may be incorrect and thus there may be no possible sequence of the mountains' heights.
In such a case, output 0.

Constraints

1 ≤ N ≤ 10^5

1 ≤ T_i ≤ 10^9

1 ≤ A_i ≤ 10^9

T_i ≤ T_{i+1} (1 ≤ i ≤ N - 1)

A_i ≥ A_{i+1} (1 ≤ i ≤ N - 1)

Input

The input is given from Standard Input in the following format:

N
T_1 T_2 ... T_N
A_1 A_2 ... A_N

Output

Print the number of possible sequences of the mountains' heights, modulo 10^9 + 7.

Sample Input 1

5
1 3 3 3 3
3 3 2 2 2

Sample Output 1

4

The possible sequences of the mountains' heights are:

1, 3, 2, 2, 2

1, 3, 2, 1, 2

1, 3, 1, 2, 2

1, 3, 1, 1, 2

for a total of four sequences.

Sample Input 2

5
1 1 1 2 2
3 2 1 1 1

Sample Output 2

0

The records are contradictory, since Mr. Takahashi recorded 2 as the highest peak after climbing all the mountains but Mr. Aoki recorded 3.

Sample Input 3

10
1 3776 3776 8848 8848 8848 8848 8848 8848 8848
8848 8848 8848 8848 8848 8848 8848 8848 3776 5

Sample Output 3

884111967

Don't forget to compute the number modulo 10^9 + 7.

Sample Input 4

1
17
17

Sample Output 4

1

Some mountain ranges consist of only one mountain.

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

{-# OPTIONS_GHC -O2 #-}
{-# LANGUAGE NumDecimals #-}
module Main (main) where
import Data.List
-- import Debug.Trace
import qualified Data.ByteString             as S
import qualified Data.ByteString.Char8       as S
import Data.Maybe (fromJust)
getInts :: IO [Int]
getInts = fmap readInts S.getLine

readInts :: S.ByteString -> [Int]
readInts = map (fst . fromJust . S.readInt). S.words

main :: IO ()
main = do
  n:_ <- getInts
  ts <- getInts
  as <- getInts
  print $ solve n ts as
  return ()
solve :: Int -> [Int] -> [Int] -> Int
solve n ts as
  | n == 1 = if head ts == head as
             then 1 else 0
  | otherwise = prod' s12
  where
    s1 = determine ts
    s2 = reverse $ determine $ reverse as
    s12 = zipWith f s1 s2
      where
        f (a,False) (b,False)        = min a b
        f (a,True) (b,True) | a /= b = 0
        f _ _                        = 1

prod' :: [Int] -> Int
prod' = foldl f 1
  where
    f a b = (a * b) `mod` (1e9 + 7)

determine :: [Int] -> [(Int,Bool)]
determine xs = (head xs,True) : zip (tail xs) sublist
  where
    sublist = zipWith (/=) xs $ tail xs