module Main where

import Control.Monad (guard)
import Data.Array.Unboxed (listArray, (!), UArray)

main :: IO ()
main = print =<< solve <$> readLn <*> getLine

solve :: Int -> [Char] -> Integer
solve n s = let (us, ms) = foldr step ([], []) $ zip s [0 ..]
                charArr = listArray (0, n-1) s :: UArray Int Char
            in  sum $ umg charArr n us ms

step :: (Char, Int) -> ([Int], [Int]) -> ([Int], [Int])
step ('U', i) (u, m) = (i:u, m)
step ('M', i) (u, m) = (u, i:m)
step _ acc = acc

umg :: UArray Int Char -> Int -> [Int] -> [Int] -> [Integer]
umg a n us ms = do
  i <- us
  j <- ms
  guard (i < j)
  let k = i + (j - i) * 2
  guard (k < n)
  guard (a!k == 'G')
  return 1