n = gets.to_i
s = gets.chomp
ans = 0
(0...n-2).each do |i|
  next unless s[i] == 'U'
  ((i+1)...n-1).each do |j|
    next unless s[j] == 'M'
    if s[j+j-i] == 'G'
      ans += 1
    end
  end
end
puts ans