Sieve Algorithm

#include<iostream>
using namespace std;

int main()
{
    int n, i, j, a[1000];

    cout<<"Enter The Limit = ";
    cin>>n;

    for(i=1; i<=n; i++)
    {
        a[i]=i;
    }

    for(i=2; i<=n; i++)
    {
        if(a[i] != -1)
        {
            for(j=2*i; j<=n; j=j+i)
                a[j]= -1 ;
        }
    }

    cout<<"Prime numbers =  ";
    for(i=2; i<=n; i++)
    {
        if(a[i] != -1)
           cout<<" "<< i ;
    }

}