n = gets.to_i
line = gets.chomp.split("")

count = 0
line.each_with_index do |v, i|
  if v == 'M'
    head, tail = line[0, i].reverse, line[i + 1, n]
    size = [head.count, tail.count].min
    size.times do |j|
      count += 1 if head[j] == 'U' && tail[j] == 'G'
    end
  end
end
puts count