Recersive Function in C++

Generate a Fibonacci series between 0 and 1000. The first two initial value is 0 and 1


#include<iostream>
using namespace std;

class fibonacci
{
public:
void setnum(int a, int b)
{
    n1=a;
    n2=b;
 
}
protected:
    int n1;
    int n2;
    int n3;
};

 class series:public fibonacci
 {
     public:
void get_series()
 {
    cout << "The Fibonacci Series  is:  \n";
    while (n1+n2<1000)
    {
        n3 = n1 + n2;
        n1 = n2;
        n2 = n3;
        cout << n3 << "  ";
    }

 }
 };

 int main()
 {
     series s;
     s.setnum(0,1);
     s.get_series();
 }