#include <bits/stdc++.h>
using namespace std;
int n, ma[10001];
void sang()
{
    for(int a = 2; a < 10000; a++)
        ma[a] = 1;
    for(int a = 2; a < 10000; a++)
        if(ma[a])
            for(int b = a*a; b < 10000; b += a)
                ma[b] = 0;
}
int main() 
{
    cin >> n;
    sang();
    for(int a = 2; a <= n; a++)
        if(ma[a]) cout << a << " ";
    return 0;
}

$#khanhtaon$

C1:

#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N = 1e6 + 7;
void Solve()
{
    int n;  cin >> n;
    vector<int> dd(N, 1);
    dd[0] = dd[1] = 0;
    for (int i = 2; i * i <= N; i++)
    {
        if (dd[i] == 1)
        {
            for (int j = i * i; j <= N; j += i) dd[j] = 0;
        }
    }
    for (int i = 2; i < n; i++)
    {
      if (dd[i] == 1) cout << i << " ";
    }
}
signed main()
{
    Solve();
    return 0;
}

C2:

#include <bits/stdc++.h>
using namespace std;
int Check(int n)
{
  if (n < 2) return false;
  int k = sqrt(n);
  for (int i = 2; i <= k; i ++)
  {
    if (n % i == 0) return false;
  }
  return true;
}
int main()
{
  int n; cin >> n;
  for (int i = 2; i < n; i ++)
  {
    if (Check(i)) cout << i << " ";
  }
}

C3:

#include <bits/stdc++.h>
using namespace std;
int main()
{
    int n; cin >> n;
    for (int i = 2; i < n; i++)
    {
        bool Check = true;
        int k = sqrt(i);
        for (int j = 2; j <= k; j++)
        {
            if (i % j == 0)
            {
                Check = false;
                break;
            }
        }
        if (Check) cout << i << " ";
    }
}