N = gets.to_i
S = gets.chomp

count = 0
N.times do |offset|
  (1 .. S.size / 2).each do |d|
    break unless offset + 2 * d < S.size
    count += 1 if S[offset] == 'U' && S[offset + d] == 'M' && S[offset + 2 * d] == 'G'
  end
end
puts count