#include<iostream>
using namespace std;
int sushu(int a)
{
	int flag = 1;
	for (int i = 2; i < sqrt(a)+1; i++)
	{
		if (a%i == 0)
		{
			flag = 0;
			break;
		}
	}
	return flag;
}
int main()
{
	int n;
	while (cin >> n)
	{
		int ans = 0, flag = 1;
		if (n == 1)
			cout << ans << endl;
		else
		{
			for (int i = 2; i <= n; i++)
			{
				flag = sushu(i);
				if (flag)
					ans++;
			}
			cout << ans+1 << endl;
		}
	}
	return 0;
}
