C语言编一个程序完成64位数据(无符号)的加法，减法运算

C语言编一个程序完成64位数据(无符号)的加法，减法运算
方法一：

#include<stdio.h>
#include<malloc.h>
#define len sizeof(struct Long) 
struct Long
{
 int data;
 struct Long *next;
};
struct Long *insert(struct Long *u,int m)
{
 struct Long *v;
 v=(struct Long *)malloc(len);
 v->data=m;
 u->next=v;
 return(v);
}
struct Long *input()
{
 struct Long *s,*ps,*qs;
 struct num
 {
  int num;
  struct num *np;
 }*p,*q;
 int i,j,k;
 long sum;
 char c;

 p=NULL;
 while((c=getchar())!='\n')
 if(c>='0'&&c<='9')
 {
  q=(struct num *)malloc(sizeof(struct num));
     q->num=c-'0';
  q->np=p;
  p=q; 
 }
 s=(struct Long *)malloc(len);
 s->data=-1;
 ps=s;
 while(p!=NULL)
 {
  sum=0;
  i=0;
  k=1;
  while(i<4&&p!=NULL)
  {
   sum=sum+k*(p->num);
   i++;
   p=p->np;
   k=k*10;
  }
  qs=(struct Long *)malloc(len);
  qs->data=sum;
  ps->next=qs;
  ps=qs;
 }
 ps->next=s;