#include <iostream>
#include<cmath>
using namespace std;
int c[1000005];
int main()
{
    c[0] = c[1] = 1;
    for(int i = 2;i<=1414;i++)
        if(c[i] == 0)
            for(int j = 2; i * j <=2000000; ++j)
                c[i * j] = 1;
    int n;
    int cnt=0;
    cin >> n;
    for(int i = 1; i <= n; ++i)
    {
        if(c[i] == 0)
            cnt++;
    }
    cout << cnt;
    return 0;
}