#include <stdio.h>
#include <stdlib.h>
int N, i,d,flag=1,j,q;
using namespace std;

int main()
{
    FILE * f;  f=fopen("ciur.in","r"); FILE * g; g=fopen("ciur.out","w"); fscanf(f,"%d",&N);
    for(i=2;i<N;++i)
    {
        if(i%2!=0)
        {
            for(d=3;d*d<=N;d+=2)
            {
                if(N%d!=0) flag=1;
                else flag=0;
            }
        }
        else flag=0;

        if(flag==1) q++;
    }
    fprintf(g,"%d",q); fclose(f); fclose(g);
    return 0;
}