#include <stdio.h>
struct list {
  int pow,coef;
  struct list *next,*pre;
};
typedef struct list node;
typedef node *link;
link head,last;
void print_forward(link head) {
  link pt1;

  printf("the input polynomial ---> f(X)=");
  pt1=head;
  do {
    if (pt1->pow != 0) printf("%2dX%2d",pt1->coef,pt1->pow);
    else printf("%2d",pt1->coef);
    pt1=pt1->next; if (pt1 != head) printf("+");
  } while (pt1 != head) ;
  printf("\n");
}

void print_backward(link last) {
  link pt1;

  printf("the input polynomial ---> f(X)=");
  pt1=last;
  do {
    if (pt1->pow != 0) printf("%2dX%2d",pt1->coef,pt1->pow);
    else printf("%2d",pt1->coef);
    pt1=pt1->pre; if (pt1 != last) printf("+");
  } while (pt1 != last) ;
  printf("\n");
}

link create() {
  link pt1,pt2;
  int c,p;

  head=NULL;
  while (1) {
    printf("give me coefficient and power ?"); scanf("%d %d",&c,&p);
    if ((c == 0) && (p == 0)) break;
    pt2=(link)malloc(sizeof(node));
    if (head == NULL) { pt1=head=pt2; pt1->pre=pt1->next=pt1; }
    else { pt1->next=pt2; pt2->pre=pt1; pt1=pt2; }
    pt2->coef=c; pt2->pow=p;
  }
  if (head != NULL) { pt2->next=head; head->pre=pt2; last=pt2; }
  return head;
}

void main() {
  int c,p;
  link h1,l1;

  printf("give me the polymonial -->\n");
  h1=create(); l1=last; print_forward(h1); print_backward(l1);
}