#include <cstdio>

using namespace std;

int n,d;

bool Divizori(int a)
{
    int div=2,i=2;
    do
    {
        if(a%i==0)
            return false;
        i++;
    }
    while(i<=a/2);
    return true;
}

int main()
{
    freopen ("ciur.in","r",stdin);
    freopen ("ciur.out","w",stdout);
    scanf("%i",&n);
    for(int i=3;i<=n;i++)
    {
        if(Divizori(i))
        {
            d++;
        }
    }
    printf("%i",d+1);
    return 0;
}