local mce, mfl, msq, mmi, mma = math.ceil, math.floor, math.sqrt, math.min, math.max

local function getprimes(x)
  local primes = {}
  local allnums = {}
  for i = 1, x do allnums[i] = true end
  for i = 2, x do
    if(allnums[i]) then
      table.insert(primes, i)
      local lim = mfl(x / i)
      for j = 2, lim do
        allnums[j * i] = false
      end
    end
  end
  return primes
end

local m = io.read("*n")
local n = io.read("*n")
local c = {}
for i = 1, n do c[i] = io.read("*n") end
local primes = getprimes(m)

local t0 = -1
local t = {}
for i = 1, m - 1 do t[i] = -1 end
t[m] = 0

for i_t = m, 1, -1 do
  if 0 <= t[i_t] then
    local cnt = t[i_t] + 1
    for i_c = 1, n do
      local cost = c[i_c]
      if cost == i_t then
        if t0 == -1 then
          t0 = cnt
        else
          t0 = mma(t0, cnt)
        end
      elseif cost < i_t then
        if t[i_t - cost] == -1 then
          t[i_t - cost] = cnt
        else
          t[i_t - cost] = mma(t[i_t - cost], cnt)
        end
      end
    end -- for i_c
  end -- 0 <= t[i_t]
end -- for i_t

local normmax = t0
for i = 1, m do
  normmax = mma(normmax, t[i])
end
local primecost = 0
for i = 1, #primes do
  if 0 < t[primes[i]] then
    primecost = primecost + t[primes[i]]
  end
end
print(normmax + primecost)