#include <iostream>

using namespace std;

int main()
{
  int n;
  cin >> n;
  int count = 0;
  for (int i = 1; i < n; i++) {
    if (i * i <= n)
      count++;
    if (i * (i + 1) <= n)
      count++;
  }
  cout << count << endl;
	return 0;
}