#include<bits/stdc++.h>
#define int long long
using namespace std;

const int N = 1e8 + 5;

int n;

bool a[N];

vector < int > prime;

int ans;

void isprime()
{
	for(int i = 2;i <= n;i ++)
	{
		if(! a[i])
		prime . push_back(i) , ans ++;
		for(int j = 0;j < prime . size() && i * prime[j] <= n;j ++)
		{
			a[i * prime[j]] = true;
			if(i % prime[j] == 0)
			break;
		}
	} 
}

main()
{
	cin >> n;
	isprime();
	cout << ans << '\n';
}