1 #include <bits/stdc++.h>
2 #define _for(i,a,b) for(int i = (a);i < b;i ++)
3 typedef long long ll;
4 using namespace std;
5 int N;
6 string s[30];
7 inline ll read()
8 {
9 ll ans = 0;
10 char ch = getchar(), last = ' ';
11 while(!isdigit(ch)) last = ch, ch = getchar();
12 while(isdigit(ch)) ans = (ans << 1) + (ans << 3) + ch - '0', ch = getchar();
13 if(last == '-') ans = -ans;
14 return ans;
15 }
16 inline void write(ll x)
17 {
18 if(x < 0) x = -x, putchar('-');
19 if(x >= 10) write(x / 10);
20 putchar(x % 10 + '0');
21 }
22 struct TreeNode
23 {
24 char val;
25 TreeNode *left;
26 TreeNode *right;
27 };
28 int go(char c)
29 {
30 _for(i,0,N)
31 if(s[i][0]==c)
32 return i;
33 return -1;
34 }
35 TreeNode* build(int cur,char give)
36 {
37 if(give=='*')
38 return NULL;
39 TreeNode* t = (TreeNode*)malloc(sizeof(TreeNode));
40 t->val = give;
41 t->left = build(go(s[cur][1]),s[cur][1]);
42 t->right = build(go(s[cur][2]),s[cur][2]);
43 return t;
44 }
45 void preorder(TreeNode *root)
46 {
47 if(!root)
48 return ;
49 printf("%c",root->val);
50 preorder(root->left);
51 preorder(root->right);
52 }
53 int main()
54 {
55 TreeNode* root;
56 N = read();
57 _for(i,0,N)
58 cin >> s[i];
59 root = build(0,s[0][0]);
60 preorder(root);
61 return 0;
62 }
