#include <cstdio>
#define VAL_MAX 2000000

using namespace std;
char v[2000001];
void ciur (){
    int i;
    long long j;
    v[0]=v[1]=1;
    for (i=2;i<=VAL_MAX;i++){
        if (v[i]==0){
            for (j=(long long)i*i;j<=VAL_MAX;j+=i)
                v[j]=1;
        }
    }
}
int main()
{
    FILE *fin=fopen ("ciur.in","r");
    FILE *fout=fopen ("ciur.out","w");
    int n,i,sol=0;
    ciur ();
    fscanf (fin,"%d",&n);
    for (i=1;i<=n;i++)
        sol+=v[i];
    fprintf (fout,"%d",n-sol);
    return 0;
}