def f(n)
    rest=n
    keta=1
    while 26**keta <= rest
        rest-=26**keta
        keta+=1
    end
    
    answer_without_padding = rest.to_s(26).tr("0-9a-p", "A-Z")
    "A"*(keta-answer_without_padding.size) + answer_without_padding
end

puts f(gets.to_i)