a = (?A..?Z).to_a
n = gets.strip.to_i
if n == 0
	puts a[0]
	exit
end
digit = 1
while n >= 1
	if digit == 1
		print a[n % 26]
	else
		print a[(n + 25) % 26]
	end
	n /= 26
	digit += 1
end