module Main where

solve p d m s =
    let seqH = takeWhile (>= m) $ iterate (subtract d) p
        seqT = repeat m
        sums = scanl1 (+) $ seqH ++ seqT
     in length $ takeWhile (<= s) sums

main :: IO ()
main = do
    [p, d, m, s] <- fmap (map read . words) getLine
    print $ solve p d m s