#! ruby
# yukicoder My Practice
# author: Leonardone @ NEETSDKASU
############################################################
def gs() gets.chomp end
def gi() gets.to_i end
def gss() gs.split end
def gis() gss.map(&:to_i) end
def nmapf(n,f) n.times.map{ __send__ f } end
def ngs(n) nmapf n,:gs end
def ngi(n) nmapf n,:gi end
def ngss(n) nmapf n,:gss end
def ngis(n) nmapf n,:gis end
def arr2d(h,w,v=0) h.times.map{[v] * w} end
def for2p(hr,wr,&pr) hr.each{|i|wr.each{|j| yield(i,j)}} end
def nsum(n) n * (n + 1) / 2 end
def vcount(d,r=Hash.new(0)) d.inject(r){|r,e| r[e]+=1;r} end
############################################################

class Abc
    @@al = ('A'..'Z').to_a
    def initialize()
        @a = [1]        
    end
    def inc()
        i = 0
        loop {
            @a[i] += 1
            break if @a[i] <= 26
            @a[i] = 1
            i += 1
            @a << 0 if @a.size == i
        }
    end
    def to_s() @a.reverse.map{|e| @@al[e-1]}*"" end
end

n = gi

abc = Abc.new
n.times {abc.inc}
puts abc.to_s