import Control.Monad
import Data.List


checkMax :: (Integral a) => [a] -> [a] -> a
checkMax cs ds = foldr ((+) . modm) 0 $ map modm $ zipWith (*) cs ds
modm a = a `mod` (10^9 + 7)

checkChair :: (Integral a) => a -> a
checkChair c
    | even c == True    = ce
    | odd c == True     = co
    | otherwise         = 0
    where
        ce = div c 2
        co = div c 2 + 1

main = do
    n <- readLn
    str <- replicateM n getLine
    let
        cd = map (map read . words) str :: [[Integer]]
        c = [head x | x <- cd]
        c' = map checkChair c
        d = [last x | x <- cd]
    print $ checkMax c' d