#include <fstream>
using namespace std;

ifstream cin("ciur.in");
ofstream cout("ciur.out");

int n;
int e[2000001];

int main()
{
    e[0] = e[1] = 1;
    for (int i = 4; i <= 2000000; i += 2)
        e[i] = 1;
    for (int i = 3; i <= 1414; i += 2)
        if (e[i] == 0)
            for (int j = i * i; j <= 2000000; j += i)
                e[j] = 1;

    e[0] = e[1] = 0; /// 0 numere prime mai mici sau egale cu 1
    e[2] = 1; /// 1 numar prim mai mic sau egal cu 2
    for (int i = 3; i <= 2000000; ++i)
        e[i] = e[i - 1] + (1 - e[i]);

    cin >> n;
    cout << e[n];
    return 0;
}