almost prime

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
typedef tree<ll,null_type,less_equal<ll>,rb_tree_tag,tree_order_statistics_node_update>ordered_set;
#define suni ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define endl "\n"
#define mn int main()
#define frac() cout.unsetf(ios::floatfield);cout.precision(6);cout.setf(ios::fixed,ios::floatfield);


const int mx=1e8+123;
bitset<mx>isprime;
vector<int>prime;
void primegen(int n)
{
    for(int i=3;i<=n;i+=2) isprime[i]=1;
    for(int i=3;i*i<=n;i+=2){
            if(isprime[i]){
        for(int j=i*i;j<=n;j+=(i*2))
            isprime[j]=0;
      }
    } //O(n)
    isprime[2]=1;
    prime.push_back(2);
    for(int i=3;i<=n;i+=2){
        if (isprime[i]) prime.push_back(i);
    }
}
mn
{
  suni;

  int n; cin>>n;
  int ans=0,alpm=0;
  primegen(n);
  for(int i=1;i<=n;i++){
    for(auto u : prime){
        if(u>=i) break;
        if(i%u==0) ans++;
    }
      if(ans==2) alpm++;
      ans=0;
  }
    cout<<alpm<<endl;
}