import Data.List ( elemIndices )

main :: IO ()
main = do
    s <- reverse . dropWhile (/= 'w') . reverse . dropWhile (/= 'c') <$> getLine
    putStrLn . show $ solve s

-- given an arg as "" or "c .. w"
solve :: [Char] -> Int
solve s = if null s || length ys == 1 then -1 else minimum zs
    where
        xs = elemIndices 'c' s
        ys = map succ $ elemIndices 'w' s
        zs = f ys xs
        f :: [Int] -> [Int] -> [Int]
        f _          []                 = []
        f [x]        _                  = []
        f yss@(y1:y2:ys) xss@(x:xs)     = if y1 > x 
                                            then (y2 - x) : f yss xss
                                            else f (y2:ys) xss