--https://www.lua.org/pil/11.4.html
local List = {}
function List.new ()
  return {first = 0, last = -1}
end

function List.pushleft (list, value)
  local first = list.first - 1
  list.first = first
  list[first] = value
end

function List.pushright (list, value)
  local last = list.last + 1
  list.last = last
  list[last] = value
end

function List.popleft (list)
  local first = list.first
  if first > list.last then return false end
  local value = list[first]
  list[first] = nil
  list.first = first + 1
  return value
end

function List.popright (list)
  local last = list.last
  if list.first > last then return false end
  local value = list[last]
  list[last] = nil
  list.last = last - 1
  return value
end

----------

local n=io.read("n")
local que=List.new()

local ts=26
while n>0 do
    List.pushleft(que,n%ts)
    n=n//26
end

local answer={}
while true do
    local pop=List.popleft(que)
    if not pop then
        break
    end
    table.insert(answer,string.char(pop+96))
end
print(table.concat(answer,""))