#include <iostream>
using namespace std;

//??¨??????????????????????????§?´???°??¨?????????
//?´???°??¨??¨?´???????????????£?????????????????§??¨????????????

const int MAX_V = 10000000;
int prime[MAX_V + 1]; //?´???°??¨
int sum[MAX_V + 1]; //?´???°?????°???????¨?

int main()
{
	int i, k, v;
	prime[0] = prime[1] = 0;
	for (i = 2; i <= MAX_V; i++)
	{
		prime[i] = 1;
	}
	for (i = 2; i*i <= MAX_V; i++)
	{
		if (prime[i])
		{
			for (k = 2 * i; k <= MAX_V; k += i)
			{
				prime[k] = 0;
			}
		}
	}

	sum[0] = 0;
	for (i = 0; i < MAX_V + 1; i++)
	{
		sum[i+1] = sum[i] + prime[i+1];
	}

	int input;
	while (cin >> input)
	{
		cout << sum[input] << endl;
	}

	return 0;
}