local function lltonumber(str)
  local ret = 0LL
  local sign = str:sub(1, 1) ~= "-"
  local begin = sign and 1 or 2
  for i = begin, #str do
    ret = ret * 10LL
    ret = ret + tonumber(str:sub(i, i))
  end
  if not sign then ret = ret * -1LL end
  return ret
end

local n = io.read("*n", "*l")
local s = io.read()
local a = 1
for ss in s:gmatch("%d+") do
  local p = lltonumber(ss)
  if p == 0LL then
    a = -1
    break
  else
    p = p % 9LL
    local str = tostring(p):gsub("LL", "")
    local p32 = tonumber(str)
    a = (a * p32) % 9
  end
end
if a == -1 then
  print(0)
elseif a == 0 then
  print(9)
else
  print(a)
end