local mfl, mce = math.floor, math.ceil
local n = io.read("*n", "*l")
local t = {}
for i = 1, n do
  local s = io.read()
  t[s] = true
end
local a = {"i", "a", "a", "e", "u", "u"}
local b = {"n", "b", "m", "g", "r"}

local function getpattern(n, patall, idx)
  local used = {}
  local retary = {}
  local div = patall
  for i = 1, n do used[i] = false end
  for i = n, 1, -1 do
    div = mfl(div / i)
    local v_idx = mfl(idx / div)
    idx = idx % div
    local tmp_idx = 0
    for j = 1, n do
      if not used[j] then
        if tmp_idx == v_idx then
          table.insert(retary, j)
          used[j] = true
          break
        else
          tmp_idx = tmp_idx + 1
        end
      end
    end
  end
  return retary
end

for i = 0, 719 do
  local pa = getpattern(6, 720, i)
  for j = 0, 119 do
    local pb = getpattern(5, 120, j)
    local z = {}
    for k = 1, 5 do
      table.insert(z, a[pa[k]])
      table.insert(z, b[pb[k]])
    end
    table.insert(z, a[pa[6]])
    z = table.concat(z)
    if not t[z] then print(z) os.exit() end
  end
end
print("NO")