Deret aritmatika c++

#include <cstdlib>

#include <iostream>

using namespace std;

class aritmatika{

friend istream& operator>>(istream&, aritmatika&);

friend ostream& operator<<(ostream&, aritmatika&);

public:

aritmatika();

void cetak();

void suku();

void jumlah();

private:

int x[100];

int a,b,n,un,sn;

};

istream& operator>>(istream& mlebu, aritmatika& s){

cout<<”Masukkan Suku Pertama :”; mlebu>>s.a; cout<<endl;

cout<<”Masukkan Beda :”; mlebu>>s.b; cout<<endl;

cout<<”Masukkan Jumlah Suku :”; mlebu>>s.n; cout<<endl;

return mlebu;

}