hdu 1598

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <vector>
#include <map>
#include <set>
#include <string>
#include <cstring>
#include <list>
#include <queue>
#include <stack>
#include <cmath>

using namespace std;

#define PF(x) (scanf("%d",&x))
#define PT(x,y) (scanf("%d%d",&x,&y))
#define PR(x) (printf("%d\n",x))
#define PRT(x,y)(printf("%d %d\n",x,y))
#define PB(x)(scanf("%I64d",&x))
#define PRB(x)(printf("%I64d\n",(x)))
typedef __int64 LL;
#define N 1005
#define M 205
#define Mod 1000
#define Inf 0x7fffffff

struct P
{
    int s,t,speed;
    void in()
    {
        PT(s,t);
        PF(speed);
    }
};

int ar[M];
P edge[N];
int n,m;

int cmp(P & a,P & b)
{
    return a.speed<b.speed;
}
int find(int a)
{
    int r = a;
    while(ar[r] != r)
    {
        r = ar[r];
    }
    return r;
}
void init()
{
    while(scanf("%d%d",&n,&m)==2)
    {
        for(int i=0;i<m;i++)
            edge[i].in();
        sort(edge,edge+m,cmp);

        int q;
        PF(q);
        for(int i=0;i<q;i++)
        {
            int s,t;
            PT(s,t);
            int mins = Inf;
            for(int k=0;k<m;k++)
            {
                for(int j=0;j<=n;j++)
                {
                    ar[j] = j;
                }

                for(int j=k;j<m;j++)
                {
                    int a = find(edge[j].s);
                    int b = find(edge[j].t);

                    ar[b] = a;
                    if(find(t) == find(s))
                    {
                        if(mins>edge[j].speed - edge[k].speed)
                            mins = edge[j].speed - edge[k].speed;
                        break;
                    }
                }
                if(mins == Inf) break;
            }
            if(mins == Inf)
            {
                puts("-1");
            }
            else PR(mins);
    
        }
    }
    return ;
}

int main()
{
    init();
    return 0;
}