1 #include<cmath>
2 #include<vector>
3 #include<cstdio>
4 #include<cstring>
5 #include<iostream>
6 #include<algorithm>
7 using namespace std;
8
9 vector<int > g[40010];
10 int len,a[80020],dep[80020],pos[80020][17],dp[80020][17],vis[80020],cnt[80020];
11
12 void dfs(int u,int fa,int deep)
13 {
14 a[++len]=u;
15 dep[len]=deep+1;
16 if(!vis[u])
17 {
18 cnt[u]=len;
19 vis[u]=1;
20 }
21 int sz=g[u].size();
22 for(int i=0; i<sz; i++)
23 {
24 if(g[u][i]!=fa)
25 {
26 dfs(g[u][i],u,deep+1);
27 a[++len]=u;
28 dep[len]=deep+1;
29 }
30 }
31 }
32
33 int main()
34 {
35 int t;
36 scanf("%d",&t);
37 while(t--)
38 {
39 int n,m;
40 len=0;
41 memset(a,0,sizeof(a));
42 memset(dep,0,sizeof(dep));
43 memset(pos,0,sizeof(pos));
44 memset(dp,0,sizeof(dp));
45 memset(vis,0,sizeof(vis));
46 memset(cnt,0,sizeof(cnt));
47 scanf("%d%d",&n,&m);
48 for(int i=1; i<=n; i++)
49 {
50 g[i].clear();
51 }
52 for(int i=1; i<=n-1; i++)
53 {
54 int from,to;
55 scanf("%d%d",&from,&to);
56 g[from].push_back(to);
57 g[to].push_back(from);
58 }
59 dfs(1,0,0);
60 printf("%d\n",len);
61 for(int i=1; i<=len; i++)
62 {
63 dp[i][0]=dep[i];
64 pos[i][0]=i;
65 }
66 for(int j=1; j<=17; j++)
67 {
68 for(int i=1; i<=len; i++)
69 {
70 if(i+(1<<(j-1))>=len)
71 {
72 break;
73 }
74 if(dp[i][j-1]>dp[i+(1<<(j-1))][j-1])
75 {
76 dp[i][j]=dp[i+(1<<(j-1))][j-1];
77 pos[i][j]=pos[i+(1<<(j-1))][j-1];
78 }
79 else
80 {
81 dp[i][j]=dp[i][j-1];
82 pos[i][j]=pos[i][j-1];
83 }
84 }
85 }
86 for(int i=1; i<=m; i++)
87 {
88 int x,y;
89 scanf("%d%d",&x,&y);
90 int dx=cnt[x];
91 int dy=cnt[y];
92 if(dx>dy)
93 {
94 swap(dx,dy);
95 swap(x,y);
96 }
97 int k=(int)(log((double)(dy-dx+1))/log(2.0));
98 int p;
99 if(dp[dx][k]>dp[dy-(1<<k)+1][k])
100 {
101 p=pos[dy-(1<<k)+1][k];
102 }
103 else
104 {
105 p=pos[dx][k];
106 }
107 printf("%d\n",a[p]);
108 }
109 }
110
111 }
