#include <stdio.h>
#include <bitset>

using namespace std;

long n,i,j,p[700000],q;
bitset <10000001>prim;
//char prim[10000001];

int main(){
    //freopen("prim.in","r",stdin);
    freopen("prim.out","w",stdout);

    n=10000000;

    //prim.set();
    prim[1]=1;
    for (i=3;i<=n;i+=2)
        if (!prim[i]){
            p[++q]=i;
            for (j=3*i;j<=n;j+=2*i)
                prim[j]=1;
        }
    printf("%ld\n",q);
    //for (i=1;i<=q;i++)
    //    printf("%ld ",p[i]);

return 0;
}