#include<fstream>
using namespace std;
ifstream f("ciur.in");
ofstream g("ciur.out");

bool v[2000002];
int k=0,val;

void ciur(int x)
{
    v[0]=v[1]=1;
    k=2;
    int i,j;
    for(i=4;i<=x;i+=2)
    {
        v[i]=1;
        k++;
    }
    for(i=3;i*i<=x;i+=2)
    {
        if(v[i]==0)
            for(j=i*i;j<=x;j+=2)
            {
                v[j]=1;
                k++;
            }
    }
    val=x+1-k;
}

int main()
{
    int x;
    f>>x;
    ciur(x);
    g<<val;
    return 0;
}