n = io.read("*n")
local rep = 1
while true do
  local mul = 1
  for i = 1, rep do
    mul = mul * 26
  end
  if n <= mul then
    local z = n - 1
    local s = {}
    for i = 1, rep do
      s[i] = string.char(z % 26 + 97)
      z = z // 26
    end
    print(table.concat(s):reverse())
    break
  else
    n = n - mul
    rep = rep + 1
  end
end
