n = gets.to_i
cl = [*?a..?z]
c = 0
while n > 0
  i = 0
  i += 1 while i * i <= n
  i -= 1
  ([*0...i] + [*0...i-1].reverse).each do |j|
    printf(cl[(c + j%2) % 26])
  end
  n -= i * i
  c = (c + 2) % 26
end
puts