local mod = 1000000007
local mfl = math.floor

local function bmul(x, y)
  local x0, y0 = x % 31623, y % 31623
  local x1, y1 = mfl(x / 31623), mfl(y / 31623)
  return (x1 * y1 * 14122 + (x1 * y0 + x0 * y1) * 31623 + x0 * y0) % mod
end

local function modpow(src, pow)
  local res = 1
  while 0 < pow do
    if pow % 2 == 1 then
      res = bmul(res, src)
      pow = pow - 1
    end
    src = bmul(src, src)
    pow = mfl(pow / 2)
  end
  return res
end

local function modinv(src)
  return modpow(src, mod - 2)
end

local function getComb(n, k)
  local ret = 1
  local inv = 1
  for i = 1, k do
    ret = bmul(ret, n + 1 - i)
    inv = bmul(inv, i)
  end
  return bmul(ret, modinv(inv))
end

local n = io.read("*n", "*l")
local s = io.read()
local t = {}
for num in s:gmatch("%d+") do
  table.insert(t, tonumber(num))
end
local k = #t
local rem = n - (k - 1)
for i = 1, k do
  rem = rem - t[i]
end
if rem < 0 then
  print("NA")
elseif k == 1 and t[1] == 0 then
  print(1)
else
  print(getComb(k + rem, rem))
end