# frozen_string_literal: true

N = gets.to_i
S = gets.chars
count = 0
(0..N - 3).each do |i|
  next unless S[i] == 'U'

  (i + 1..N - 2).each do |j|
    next unless S[j] == 'M'

    count += 1 if S[2 * j - i] == 'G'
  end
end
puts count