1 #include <iostream>
 2 #include <cstdio>
 3 #include <algorithm>
 4 using namespace std;
 5 struct node
 6 {
 7     int s,d,f;
 8 } p[1010];
 9 
10 int father[210];
11 const int INF=9999999;
12 
13 void set(int n)
14 {
15     for (int i=1; i<=n; i++)
16         father[i]=i;
17 }
18 
19 bool cmp(const node &a,const node &b)
20 {
21     return a.f<b.f;
22 }
23 
24 int find(int a)
25 {
26     if (father[a]==a)return a;
27     return father[a]=find(father[a]);
28 }
29 
30 void Union(int x,int y)
31 {
32     x=find(x);
33     y=find(y);
34     if (x!=y)
35         father[x]=y;
36 }
37 
38 int main ()
39 {
40     int n,m,Min;
41     while (~scanf("%d%d",&n,&m))
42     {
43         for (int i=1; i<=m; i++)
44         {
45             scanf("%d%d%d",&p[i].s,&p[i].d,&p[i].f);
46         }
47         sort(p+1,p+m+1,cmp);
48         int q;
49         scanf("%d",&q);
50         while (q--)
51         {
52             int a,b,ans,i,j;
53             Min=INF;
54             scanf("%d%d",&a,&b);
55             for (i=1; i<=m; i++)
56             {
57                 set(n);
58                 for (j=i; j<=m; j++)
59                 {
60                     Union(p[j].s,p[j].d);
61                     if (find(a)==find(b))
62                         break;
63                 }
64                 if(j==m+1)
65                // printf ("-1\n");
66                 break;
67                 ans=p[j].f-p[i].f;
68                 if (Min>ans)
69                 {
70                     Min=ans;
71                 }
72             }
73 
74             if(Min==INF)
75                 printf("-1\n");
76             else
77                 printf("%d\n",Min);
78         }
79     }
80     return 0;
81 }