#include <iostream>
#include <string>
using namespace std;

int main(){
int n;
cin >> n;
int a[n+1];
int b;
int c;
b=1;
while(b<n+1){
a[b]=0;
b=b+1;}
a[1]=1;
b=2;
while(b<n+1){
if(a[b]=0){ c=2; while(1){if(c*b>n){break;} a[c*b]=1; c=c+1;}}
b=b+1;}

int d;
d=0;
b=1;
while(b<n+1){
if(a[b]=0){d=d+1;}
b=b+1;}
cout << d;


}