1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<algorithm>
 5 #include<queue>
 6 using namespace std;
 7 const int MAXN=1001;
 8 const int maxn=0x7fffffff;
 9 struct node
10 {
11     int u;
12     int v;
13     int w;
14     int next;
15 }edge[MAXN];
16 int num=1;
17 int head[MAXN];
18 int dis[MAXN];
19 int n,q;
20 int vis[MAXN];
21 int spfa(int bg,int ed)
22 {
23     for(int i=1;i<=n;i++)dis[i]=maxn;
24     memset(vis,0,sizeof(vis));
25     queue<int>q;
26     q.push(bg);
27     dis[bg]=0;
28     vis[bg]=1;
29     while(q.size()!=0)
30     {
31         int p=q.front();
32         q.pop();
33         for(int i=head[p];i!=-1;i=edge[i].next)
34         {
35             int to=edge[i].v;
36             if(dis[to]>dis[p]+edge[i].w)
37             {
38                 dis[to]=dis[p]+edge[i].w;
39                 if(vis[to]==0)
40                 {
41                     q.push(to);
42                     vis[to]=1;
43                 }
44             }
45         }
46     }
47     return dis[ed];
48 }
49 int main()
50 {
51     freopen("pwalk.in","r",stdin);
52     freopen("pwalk.out","w",stdout);
53     scanf("%d%d",&n,&q);
54     for(int i=1;i<=n;i++)head[i]=-1;
55     for(int i=1;i<n;i++)
56     {
57         scanf("%d%d%d",&edge[num].u,&edge[num].v,&edge[num].w);
58         edge[num].next=head[edge[num].u];
59         head[edge[num].u]=num++;
60         edge[num].v=edge[num-1].u;
61         edge[num].u=edge[num-1].v;
62         edge[num].w=edge[num-1].w;
63         edge[num].next=head[edge[num].u];
64         head[edge[num].u]=num++;
65     }
66     for(int i=1;i<=q;i++)
67     {
68         int bg;
69         int ed;
70         scanf("%d%d",&bg,&ed);
71         printf("%d\n",spfa(bg,ed));
72     }
73     return 0;
74 }