> # include <stdio.h>
> int main()
> {
> 	static char a[102][72]={{"http://www.acm.org/"}},b[8];
> 	int i,j;
> 	for(i=0;;)
> 		{
> 			scanf("%s",b);
> 			if(*b=='Q')
> 				break;
> 			else if(*b=='V')
> 			{
> 				i++;
> 				scanf("%s",a[i]);
> 				printf("%s\n",a[i]);
> 				for(j=i+1;j<102;j++)
> 					*a[j]=0;
> 			}
> 			else if(*b=='B')
> 			{
> 				i--;
> 				if(i>=0)
> 				printf("%s\n",a[i]);
> 				else {i++;
> 					printf("Ignored\n");
> 					}
> 			}
> 			else if(*b=='F')
> 			{
> 				i++;
> 				if(*a[i]!='\0')
> 				printf("%s\n",a[i]);
> 				else printf("Ignored\n");/////===>>>没有还原
> 			}
> 		}
> 	return 0;
> }
> 
>