function len(t) local r = 0 for k,v in pairs(t) do r = r + 1 end return r end

print((function (y, n)
	for i=0,9 do n[tostring(i)] = true end

	for _=1,tonumber(io.stdin:read("*l")) do
		local s = io.stdin:read("*l")

		if s:sub(9) == "NO" then
			for e in s:gmatch("%d") do y[e],n[e] = nil,nil end
		else
			if next(y) == nil then
				for e in s:gmatch("%d") do if n[e] ~= nil then y[e] = true end end
			else
				for k,_ in pairs(y) do
					if s:find(k) == nil then y[k],n[k] = nil,nil end
				end
				for e in s:gmatch("%d") do if y[e] == nil then n[e] = nil end end
			end
		end
	end

	return string.format("%s", next(len(y) == 1 and y or n))
end)({}, {}))