import Control.Applicative ((<$>))
import Control.Monad (replicateM)
import Data.List

import Data.Char (isSpace)
import Data.ByteString.Char8 (ByteString)
import qualified Data.ByteString.Char8 as B

main :: IO ()
main = do
  n <- readLn
  solve n <$> replicateM n getIntegerList >>= print

solve :: Int -> [[Integer]] -> Integer
solve n = foldl' f 0
  where
    m = 1000000007
    f sn [c, d] = ((let c' = c `div` 2 in if even c then c' else c' + 1) * d + sn) `mod` m

getIntegerList :: IO [Integer]
getIntegerList = unfoldr f <$> B.getLine
  where
    f s = do
      (n, s') <- B.readInteger s
      return (n, B.dropWhile isSpace s')