كمك براي رفع خطا برنامه

برنامه انجام + -* چند جمله اي با كلاس
من تا جايي كه تونستم نوشتم اگه كسي بلده كمكم كنه تا كامل بشه
ممنون

#include <iostream.h>
#include <string.h>
#include <iomanip.h>
class Polynomial{
private :
int k;
int a[25];
int n[25];
public:
friend class Polynomial;
friend ostream & operator << ( ostream &, const Polynomial & );
friend istream & operator >> ( istream &, Polynomial & );

friend Polynomial operator + ( Polynomial&, Polynomial & );
friend Polynomial operator - ( Polynomial&, Polynomial & );
friend Polynomial operator * ( Polynomial&, Polynomial & );
Polynomial();
Polynomial(int);
};
Polynomial::Polynomial(){
for (int i=0;i<25;i++){
a[i]=0;
n[i]=0;
k=0;
}
}
Polynomial::Polynomial( int v){
k=v;
for(int i=0;i<25;i++) {
a[i]=0;
n[i]=0;
}
}
istream & operator >> ( istream & input, Polynomial & y )
{
for (int i=0;i<x.k;i++) {
input>>set(1)>>x.a[i];
input.ignore(2);
input>>set(1)>>x.n[i];
input.ignore();
}
}
ostream & operator << ( ostream & output, Polynomial & x )
{
for(int i=0;i<25 &&x.a[i]!=0;i++)
output<< x.a[i]<<"x^"<<x.n[i]<<"+";
output<<endl;
}
Polynomial operator + ( Polynomial &x, Polynomial &y ){
Polynomial z;
for(int i=0;i<5;i++){
z.a[i]=x.a[i]+y.a[i];
z.n[i]=x.a[i];
i.n[i]=y.a[i];
}
}
Polynomial operator - ( Polynomial &x, Polynomial &y ){
Polynomial z;
for(int i=0;i<5;i++){
z.a[i]=-(y.a[i]);
i.a[i]=x.a[i]+y.a[i];
i.n[i]=x.n[i];
z.n[i]=y.n[i];
}
}

Polynomial operator *( Polynomial &x, Polynomial &y )
{
Polynomial z;
int c=0;
for(int j=0;j< x.k;j++){
for(int i=0;i<y.k;i++){
z.a[i+c]=x.a[j]*y.a[i];
z.n[i+c]=x.n[j]+y.n[i];
}
c=c+x.k;
}
}
void main()
{
polynomial y(6),x(3);
y.input();
x.input();
polynomial k=y+x;
k.print();
polynomial k=y-x;
k.print;
polynomial k=y*x;
k.print();
polynomial p6=(p1-p2)*(p1+p2);
p6.print;
polynomial p7=p1.drivate();
p7.print();
p7.print value(1);
}