-- Try yukicoder
-- author: Leonardone @ NEETSDKASU

main = getContents >>= putStrLn . solve . map read . words


solve (x:y:n:xs) = calc xs where
    calc (i:j:ys)
        | i * y <= j * x = calc (j:ys)
        | otherwise = "NO"
    calc _ = "YES"