# Sieve of Eratosthenes

/**
  * 에라토노스의 체
  * @param n
  * @return
  */
public static int solution(int n) {
  boolean[] b = new boolean[n + 1];
  int answer = 0;

  for (int i = 2; i <= n; ++i) {
    if (b[i] == false) {
      answer++;
      for (int j = i; j <= n; j += i) {
        b[j] = true;
      }
    }
  }

  return answer;
}