main :: IO ()
main = do
    n <- getLine
    s <- getLine
    print $ solve s 0

solve :: String -> Int -> Int
solve [] acc = acc
solve xs acc | length xs < 3 = acc
solve xs@('U' : xs') acc = solve (getNext xs) (acc + c)
    where steps = getSteps xs 0
          c = foldl (\acc' step -> if findUMG xs 0 step == Found then acc' + 1 else acc') 0 steps
solve xs acc = solve (getNext xs) acc

data UMG = Found | NotFound | Over deriving (Show, Eq)

findUMG :: String -> Int -> Int -> UMG
findUMG s start step = if start + step + step + 1 > length s
    then Over
    else if s !! start == 'U' && s !! (start+step) == 'M' && s !! (start+step*2) == 'G' then
        Found
    else
        NotFound

getNext :: String -> String
getNext (x : xs) = dropWhile (/= 'U') xs

getSteps :: String -> Int -> [Int]
getSteps [] start = []
getSteps (x : []) start = []
getSteps (x : xs) start =
    if length d > 0 then start + i : getSteps d (start + i) else getSteps (drop 1 d) (start + i)
    where d = dropWhile (/='M') xs
          i = length xs - length d + 1