import Data.List

anyKadomatsu as = any (== (head as)) (tail as) || any (== (last as)) (init as)

isKadomatsu (x:y:z:zs) = ( (x > y) && (z > y) ) || ( (x < y) && (z < y) )

solve as
    | anyKadomatsu as   = 0     -- おなじ長さの竹があるので門松でない
    | isKadomatsu as    = -1    -- すでに門松なので、無限門松
    | otherwise         = mottoKadomatsu ((last . sort) as) as  -- 有限門松
    where
        mottoKadomatsu 0 _  = 0
        mottoKadomatsu p as = x + mottoKadomatsu (p - 1) as
            where
                bs = map (`mod` p) as
                x   | not (anyKadomatsu bs) && isKadomatsu bs   = 1
                    | otherwise                                 = 0

answer a
    | a == -1   = "INF"
    | otherwise = show a

main = do
    as <- map (read :: String -> Int) . words <$> getLine
    putStrLn $ answer $ solve as