> #include<iostream>
> #include<string>
> #include<stack>
> using namespace std;
> int main()
> {
> 	stack<string>fostack,bastack;
> 	string s,page,curpage;
> 	int i;
> 	curpage="http://www.acm.org/";
> 	while(cin>>s,s[0]!='Q')
> 	{
> 		if(s[0]=='V')
> 		{
> 			cin>>page;
> 			bastack.push(curpage);
> 			curpage=page;
> 			cout<<curpage<<endl;
> 			if(!fostack.empty())
> 			{
> 				for(i=0;i<fostack.size();i++)
> 					fostack.pop();
> 			}
> 		}
> 		if(s[0]=='B')
> 		{
> 			if(!bastack.empty())
> 			{
> 				fostack.push(curpage);
> 				curpage=bastack.top();
> 				bastack.pop();
> 				cout<<curpage<<endl;
> 			}
> 			else
> 				cout<<"Ignored"<<endl;
> 
> 		}
> 		if(s[0]=='F')
> 		{
> 			if(!fostack.empty())
> 			{
> 				bastack.push(curpage);
> 				curpage=fostack.top();
> 				fostack.pop();
> 				cout<<curpage<<endl;
> 			}
> 			else
> 				cout<<"Ignored"<<endl;
> 		}
> 	}
> 	return 0;
> }