#include <stdio.h>
#include <math.h>
#define max 2000002

char v[max];
long n,count,i,j,indice;

FILE *f,*g;

int main(){

f=fopen("ciur.in","r");
g=fopen("ciur.out","w");

fscanf(f,"%ld",&n);

for(i=3;i<=n;i+=2)
   if(!v[i]&&i%2) {
    count++;indice=i;
    for(j=i*indice;j<=n;j*=indice)  { v[j]=1; indice+=2; }
   } 

fprintf(g,"%ld\n",count+1);
fclose(g);
return 0;
}