Эратосфен

#include "stdafx.h"
#include <iostream>

using namespace std;

int main() {
    int n;
    cout << "n= ";
    cin >> n;
    int *a = new int[n + 1];
    int i;
    for (i = 0; i < n + 1; i++)
        a[i] = i;
    for (int p = 2; p < n + 1; p++)
    {
        if (a[p] != 0)
        {
            for (int j = p * p; j < n + 1; j=j+p)
                a[j] = 0;
        }
    }
    for (i = 0;i < n + 1;i++)
        if (a[i] != 0) cout << a[i] << " ";
}