import Data.Array
import Data.List

main :: IO ()
main = do
    n <- getLine
    s <- getLine
    let cs = array (0,length s - 1) [a | a <- zip [0..] s]
    print $ solve cs

solve :: Array Int Char -> Int
solve cs = foldl' (\acc1 ui ->
    if cs!ui == 'U' then
        acc1 + foldl' (\acc2 gi ->
            if cs!gi == 'M' && gi+gi-ui < length cs && cs!(gi+gi-ui) == 'G' then
                acc2+1
            else
                acc2
            ) 0 [ui..length cs -1]
    else
        acc1
    ) 0 [0..length cs - 2]