defmodule Main do
    def is_g(s, diff) do
        cond do
            diff >= String.length(s) -> 0
            String.at(s, diff) == "G" -> 1
            true -> 0
        end
    end

    def find_m("", _), do: 0
    def find_m(s, diff) do
        remain = String.slice(s, 1..-1)
        case String.at(s, 0) do
            "M" -> is_g(remain, diff) + find_m(remain, diff + 1)
            _ -> find_m(remain, diff + 1)
        end
    end


    # U
    def find_u(""), do: 0
    def find_u(s) do
        remain = String.slice(s, 1..-1)
        case String.at(s, 0) do
            "U" -> find_m(remain, 0) + find_u(remain)
            _ -> find_u(remain)
        end
    end

    def solve(s) do
        find_u(s)
    end


    def main do
        _ = IO.gets("")
        IO.gets("") |> String.trim |> solve |> IO.puts
    end
end