#include <iostream>
#include <stdio.h>
using namespace std;
FILE *f,*g;
int v[102];
int main()
{
    f=fopen("ciur.in","r");
    g=fopen("ciur.out","w");
    int n,d,s=0;
    fscanf(f,"%d",&n);
    for(int i=2;i<=n;i++) //cirul lui erastorene
    {
        for(int j=i*2;j<=n;j+=i)
        {
            if (!(j%i)) ///in mod normal, de la comp. j%i=1 (gen true sau false) daca negam <exp._logica> va fi 0
            {
                v[j]=1;
            }
        }
        if(v[i]==0)
            s++;
    }
    fprintf(g,"%d",s);
    fclose(f);
    fclose(g);
    return 0;
}