maxExaminees :: [[Integer]] -> Integer
maxExaminees = (`mod` 1000000007) . sum . map (`mod` 1000000007) .
    map (\(c : d : _) -> (*) d $ (`mod` 1000000007) $ (c + 1) `div` 2)

main :: IO ()
main = getLine >> getContents >>= print .
    maxExaminees . map (map read) . map words . lines