C++
#include<iostream>
using namespace std;
const int N = 100010;
int head, e[N], ne[N], idx;
void init()
{
head = -1;
idx = 0;
}
void add(int k, int x)
{
e[idx] = x;
ne[idx] = ne[k];
ne[k] = idx;
idx ++;
}
void remove(int k)
{
ne[k] = ne[ne[k]];
}
void add_to_head(int x)
{
e[idx] = x;
ne[idx] = head;
head = idx;
idx ++;
}
int main()
{
int m;
cin >> m;
init();
while(m--)
{
int k, x;
char op;
cin >> op;
if(op == 'H')
{
cin >> x;
add_to_head(x);
}else if(op == 'D')
{
cin >> k;
if(!k) head = ne[head];
else remove(k - 1);
}else
{
cin >> k >> x;
add(k - 1, x);
}
}
for(int i = head; i != -1; i = ne[i])
cout << e[i] << ' ';
cout << endl;
return 0;
}