local mfl = math.floor

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 function lb_sq(ary, x)
  local num = #ary
  if num == 0 then return 1 end
  if(x <= ary[1] * ary[1]) then return 1 end
  if(ary[num] * ary[num] < x) then return num + 1 end
  local min, max = 1, num
  while(1 < max - min) do
    local mid = mfl((min + max) / 2)
    if(ary[mid] * ary[mid] < x) then
      min = mid
    else
      max = mid
    end
  end
  return max
end

local n = io.read("*n")
if n == 1 then print(0)
else
  local cnt = 1
  local primes = getprimes(n)
  for i = 2, #primes do
    local rsq = 2 + primes[i]
    local cand = lb_sq(primes, rsq)
    if cand <= n and primes[cand] * primes[cand] == rsq then
      cnt = cnt + 2
    end
  end
  print(cnt)
end