import Control.Applicative
import Data.Maybe
import qualified Data.ByteString.Char8 as B

calc :: (Integral t) => t -> [t] -> t
calc acc [c,d] = (acc+(c+1)`div`2*d)`mod`1000000007

main :: IO()
main = do
  getLine
  print =<< foldl calc 0 <$> map (map fst . mapMaybe B.readInteger . B.words) <$> B.lines <$> B.getContents