T = gets.to_i
x = []
T.times { x<< gets.to_i }

hantei = true
hantei = false unless x[0] == -1 or x[0] == 1

(0..T-2).each do |i|
  hantei = false unless (x[i].abs - x[i+1].abs) == 1 or -1
end

if hantei 
  puts 'T'
else
  puts 'F'
end