import math, sequtils
proc simple(limit: int): seq[int] =
  var isPrime = newSeq[bool](limit + 1)
  for i in 0..limit:
    isPrime[i] = true
  isPrime[0] = false
  isPrime[1] = false

  for i in 2..int(sqrt(float(limit))):
    if isPrime[i]:
      var j = i * i
      while j <= limit:
        isPrime[j] = false
        j += i

  result = @[]
  for i, prime in isPrime:
    if prime:
      result.add(i)

proc segmented(L, R: int): seq[int] =
  let limit = int(sqrt(float(R)))
  let primes = simple(limit)
  var isPrime = newSeq[bool](R - L + 1)
  for i in 0..<isPrime.len:
    isPrime[i] = true

  for p in primes:
    var start = (L div p) * p
    if start < L: start += p
    if start == p: start += p  

    var j = start
    while j <= R:
      isPrime[j - L] = false
      j += p

  result = @[]
  for i in 0..<isPrime.len:
    if isPrime[i] and (i + L >= 2):
      result.add(i + L)

let L = 10
let R = 500000000
echo segmented(L, R)