#include<iostream>
using namespace std;
#include<cmath>
bool prime(int a){
if(a == 1){
return 0;
}
bool flag = 1;
for(int i = 2;i <= pow(a,0.5);i++){
if(a % i == 0){
flag = 0;
break;
}
}
return flag;
}
int main(){
int cnt = 0,n;cin >> n;
for(int i = 1;i <= n;i++){
if(prime(i)){
cnt++;
}
}cout << cnt;
return 0;
}