#include <stdio.h>
#include <stdlib.h>
#define ElementType int
typedef struct Node NodeType;
struct Node {
ElementType index;
int father; // 是否为父结点
};
NodeType Error = {-1, 0};
#define MaxSize 30
typedef struct SNode *Stack;
struct SNode {
NodeType Data[MaxSize];
int Top;
}stack;
void makeEmpty()
{
stack.Top = -1;
}
void Push(NodeType item)
{
if (stack.Top == MaxSize - 1) return;
else stack.Data[++(stack.Top)] = item;
}
NodeType Pop()
{
if (stack.Top == -1) return Error;
else return (stack.Data[(stack.Top)--]);
}
NodeType getTopItem()
{
if (stack.Top == -1) return Error;
else return (stack.Data[(stack.Top)]);
}
void printPostorder(int N)
{
int i, flag;
char preStr[5] = {'\0'}, str[5] = {'\0'};
NodeType preNode, node, tmp;
makeEmpty();
flag = 0;
scanf("%s %d", preStr, &preNode.index);
for (i = 1; i < 2 * N; ++i) {
scanf("%s", str);
if (str[1] == 'u')
scanf("%d", &node.index);
if (preStr[1] == 'u') { // 只要前一次是push就可直接压栈
preNode.father = 0;
Push(preNode);
}
else { // 前一次为pop时
if (str[1] == 'o') { // 第二次也为pop时可以安全出栈并输出
tmp = Pop();
if (flag) printf(" ");
printf("%d", tmp.index);
flag = 1;
// 如果此时栈顶元素是父节点，则依次输出所有栈顶的父节点
tmp = getTopItem();
while (tmp.father) {
Pop();
if (flag) printf(" ");
printf("%d", tmp.index);
tmp = getTopItem();
}
}
else { // 第二次为push时，说明此时的栈顶元素是有右孩子的父节点，需要pop出来修改其father字段再push回栈中
tmp = Pop();
tmp.father = 1;
Push(tmp);
}
}
preStr[1] = str[1]; // 由于每次只根据第二个字符判断是push还是pop，所以只更改第二个字符即可
preNode = node;
}
// 输出栈中所有剩余结点
tmp = Pop();
while (tmp.index > 0) {
if (flag) printf(" ");
printf("%d", tmp.index);
tmp = Pop();
}
}
int main()
{
int N;
scanf("%d", &N);
printPostorder(N);
return 0;
}
