PAT 1086

//当你真的专注时，环境就不会影响到你。//永远不要当分母
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
#include<vector>
#include<queue>
#include<stack>
using namespace std;

const int maxn=40;
stack<int> s;
vector<int> op;
int pre[maxn],in[maxn];
int preL,preR,inL,inR;

struct node
{
	node* lchild;
	node* rchild;
	int data;
};

node* create(int preL,int preR,int inL,int inR)
{
	if(preL>preR)
		return NULL;
	node* root=new node;
	root->data=pre[preL];
	int i;
	for(i=inL;i<=inR;i++)
	{
		if(in[i]==pre[preL])
			break;
	}
	int numleft=i-inL;
	root->lchild=create(preL+1,preL+numleft,inL,i-1);
	root->rchild=create(preL+numleft+1,preR,i+1,inR);
	return root;
}

/*void level_traverse(node* root)
{
	queue<node*> q;
	q.push(root);
	while(!q.empty())
	{
		node* top=q.front();
		q.pop();
		op.push_back(top->data);
		if(top->lchild!=NULL)
			q.push(top->lchild);
		if(top->rchild!=NULL)
			q.push(top->rchild);
	}
}*/

void postorder(node* root)
{
	if(root==NULL)
		return;
	postorder(root->lchild);
	postorder(root->rchild);
	op.push_back(root->data);
}
int main()
{
	int n;
	char str[5];
	int j=0,k=0;
	int temp;
	scanf("%d",&n);	
	for(int i=0;i<2*n;i++)
	{
		scanf("%s",str);
		if(strcmp(str,"Push")==0)
		{
			scanf("%d",&temp);
			pre[j++]=temp;
			s.push(temp);
		}
		else 
		{
			in[k++]=s.top();
			s.pop();
		}
	}
	node* root=create(0,n-1,0,n-1);
	postorder(root);
	for(int i=0;i<op.size()-1;i++)
	{
		printf("%d ",op[i]);
	}
	printf("%d",op[op.size()-1]);
	
	system("pause");
	return 0;
}