#include <bits/stdc++.h>
int main() {
  int i, j, n, count = 0;
  scanf("%d", &n);
  for (i = 2; i <= n; i++) {
    for (j = 2; j <= i; j++) {
      if (i % j != 0)
        count++;
      else
        break;
    }
  }
  printf(" %d", count);
  return 0;
}
