1 #include<iostream>
2 #include<cstdio>
3 #include<cstring>
4 #include<cstdlib>
5 #include<algorithm>
6 #include<vector>
7 #include<stack>
8 using namespace std;
9 const int maxn=1007;
10 const int inf=0x3f3f3f3;
11 struct node
12 {
13 int to;
14 };
15 vector<node> G[maxn];
16 int root,ans[maxn],n;
17 bool flag[maxn];
18 char value[maxn];
19 void init()
20 {
21 for(int i=0;i<maxn;i++) G[i].clear();
22 memset(value,0,sizeof(value));
23 memset(flag,0,sizeof(flag));
24 memset(ans,0,sizeof(ans));
25 root=-1;
26 }
27 void input()
28 {
29 int a,b;node n1;
30 for(int i=1;i<n;i++)
31 {
32 scanf("%d%d",&a,&b);
33 n1.to=b;
34 G[a].push_back(n1);
35 n1.to=a;
36 G[b].push_back(n1);
37 }
38 scanf("%d",&root);
39 scanf("%s",value+1);
40 }
41 char dfs(int point,int father)
42 {
43 int l=G[point].size();
44 if(l==1&&point!=root) {return value[point];}
45 stack<char> str;
46 while(!str.empty()) str.pop();
47 for(int i=0;i<l;i++)
48 {
49 if(G[point][i].to==father) continue;
50 if(!flag[G[point][i].to])
51 str.push(dfs(G[point][i].to,point));
52 }
53 if(str.size()==1) value[point]=str.top();
54 else if(str.size()==3){
55 char a=str.top();str.pop();
56 char b=str.top();str.pop();
57 char c=str.top();str.pop();
58 if(b=='+') value[point]=(a-'0')+(c-'0')+'0';
59 else if(b=='-') value[point]=(a-'0')-(c-'0')+'0';
60 else if(b=='*') value[point]=(a-'0')*(c-'0')+'0';
61 }
62 return value[point];
63 }
64 int main()
65 {
66 int a,b;
67 while(~scanf("%d",&n)){
68 init();
69 input();
70 flag[root]=1;
71 dfs(root,-1);
72 int res=value[root]-'0';
73 printf("%d\n",res);
74 }
75 return 0;
76 }
77 /*
78 10
79 1 2
80 1 3
81 1 4
82 2 5
83 4 6
84 4 7
85 4 8
86 6 9
87 8 10
88 1
89 EE+E3E*E45
90 10
91 1 2
92 1 3
93 1 4
94 2 5
95 2 6
96 2 7
97 5 8
98 7 9
99 4 10
100 1
101 EE*EE+E345
102 */
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