#include<stdio.h>
int n,x,y,c,z;
int main()
{
    freopen("ciur.in","r",stdin);
    freopen("ciur.out","w",stdout);
    scanf("%d",&n);
    x=2;
    z=0;
    while(x<=n)
    {
        y=1;
        c=0;
        while(y<=x)
        {
            if(x%y==0)
            {
                c=c+1;
            }
            y=y+1;
        }
        if(c==2)
        {
            z=z+1;
        }
        x=x+1;
    }
    printf("%d",z);
    fclose(stdin);
    fclose(stdout);
    return 0;
}