MODE = "stdio"

tmp = Array.new

if(defined? MODE)
  tmp = STDIN.read.split("\n")
else
  iotmp = "\
  676
  ".split("\n")
  iotmp.each{|s|
    tmp << s.strip
  }
end

alphabet = ('A'..'Z').to_a

N = tmp[0].to_i

a = N
arr = []
while true
  b =  a%alphabet.size
  arr<<b
  a = a/alphabet.size-1
  break if a<0
end

result=""
arr.each do |n|
  result += alphabet[n]
end
puts result.reverse