#include<stdio.h>

bool a[2000001];

int main()
{
    FILE *fin,*fout;
    fin=fopen("ciur.in","r");
    fout=fopen("ciur.out","w");

    int n,counter=0;
    fscanf(fin,"%d",&n);
    a[1]=1;
    for(int i=3;i<=n/2;i++)
    {
        if(a[i]==0)
            for(int j=i*2;j<=n/2;j+=i)
                a[j]=1;
    }
    for(int i=1;i<n;i++)
        if(a[i]==0 && i%2==1)
            counter++;

    fprintf(fout,"%d",counter);

}