// C++ program to print all primes smaller than or equal to
// n using Sieve of Eratosthenes

// Time complexity O(n*log(log(n)))

#include <bits/stdc++.h>
using namespace std;

void SieveOfEratosthenes(int n)
{

    bool prime[n+1];
    memset(prime, true, sizeof(prime));

    for (int p=2; p*p<=n; p++)
    {
        // If prime[p] is not changed, then it is a prime
        if (prime[p] == true)
        {

            for (int i=p*p; i<=n; i += p)
                prime[i] = false;
        }
    }
    // Print all prime numbers
    for (int p=2; p<=n; p++)
       if (prime[p])
          cout << p << " ";
}

int main()
{
    int n=0;
    cout<< "Enter your number"<< endl;
    cin>>n;
    cout << "Following are the prime numbers smaller "
         << " than or equal to " << n << endl;
    SieveOfEratosthenes(n);
    return 0;

    // Time complexity O(n*log(log(n)))
}