local n = io.read("*n")

local function getalpha(val)
  return string.char(65 + val)
end

local digit = 1
local diglim = 26
while(diglim <= n) do
  digit = digit + 1
  n = n - diglim
  diglim = diglim * 26
end
local ret = {}
for i = 1, digit do
  local lowdig = n % 26
  table.insert(ret, 1, getalpha(lowdig))
  n = math.floor(n / 26)
end
print(table.concat(ret))