#include <bits/stdc++.h>
int main() {
  int n, A[10000], i, j, count = 0, flag;
  scanf("%d", &n);
  for (i = 2; i <= n + 1; i++) {
    flag = 0;
    for (j = 2; j <= n + 1; j++) {
      if (i % j == 0) flag++;
    }
    if (flag == 1) {
      count++;
    }
  }
  printf("%d\n", count);
  return 0;
}
