编译时出现的一个错误，请教一下

用c编的程序，编译的时候出现了三个提示一样的错误，lvalue required in function main 什么意思，估计应该在哪里修改，请各位高手指教，谢谢了
----------------解决方案--------------------------------------------------------
嗯把代码发出来看下撒,这样哪知道错在哪儿啊?
----------------解决方案--------------------------------------------------------
用*标记的句子就是报错的地方，三次报错一样
main()
{struct car{
   int inf;
   int num;
   int time;
   struct car *next;
  };
int m,n=0,j=0,time1;
int max=3;
struct car *p1,*p2;
struct car *front,*rear;
struct car *top1,*base1;
struct car *top2,*base2;
p1=(struct car*)malloc(sizeof(struct car));
top1=base1=(struct car*)malloc(3*sizeof(struct car));
top2=base2=(struct car*)malloc(sizeof(struct car));
front=rear=(struct car*)malloc(sizeof(struct car));
printf("input the information of this car:");
scanf("%d",&p1->inf);
printf("input the number of this car:");
scanf("%d",&p1->num);
printf("input the time of this car:");
scanf("%d",&p1->time);
while(p1->inf!=00)
   {while(p1->inf==01)
       {if(top1-base1<(max*sizeof(struct car)))
           { ****top1++=p1;****
             n++;
             printf("the car stopped at the %dth of the stack",n);
           }
          else
             {rear->next=p1;
              rear=p1;
              j++;
              printf("the car stopped at the %dth of the quene",j);
             }
         p1=(struct car*)malloc(sizeof(struct car));
         printf("input the information of this car:");
         scanf("%d%d%d",&p1->inf,&p1->num,&p1->time);
       }
    while(p1->inf==10)
        {while(p1->num!=(--top1)->num)
           {
           **** top2++=(--top1);*****
            time1=p1->time-(--top1->time);
            printf("the car has stopped %d minuters\n",time1);
            printf("you should pay for %d*x yuan\n",time1);
           }
         while(top2!=base2)
            top1++==(--top2);
         while(front!=rear)
            { p2=front->next;
              front->next=p2->next;
              p2->time=p1->time;
             ***** top1++=p2;*******
              if(rear==p2)
                rear=front;
              p1=(struct car*)malloc(sizeof(struct car));
              printf("input the information of this car:");
              scanf("%d%d%d",&p1->inf,&p1->num,&p1->time);
         }
     if(p1->inf==0)
      break;
    }
   printf("thank you for using this system\n");
  }
}的
----------------解决方案--------------------------------------------------------