#include <iostream>
#include <cstdlib>
#include <cstring>
#include <cstdio>
#include <cmath>

using namespace std;

const int MAXN=102;
const int MAXM=200000;
const int M=MAXN*2;
const int oo=1000000000;

struct edge
{
	int t,c;
	edge *p;
}e[MAXM],*v[MAXN];

int n,m,i,j,k,es=-1,d[MAXN],Q[MAXN*2],s,t,h,A,B;
bool iq[MAXN];

inline void addedge(int i,int j,int c)
{
	e[++es].t=j; e[es].c=c; e[es].p=v[i]; v[i]=e+es;
}

int main()
{
	freopen("rebuild.in","r",stdin);
	freopen("rebuild.out","w",stdout);
	scanf("%d%d",&n,&m);
	while (m--)
	{
		scanf("%d%d%d",&i,&j,&k);
		addedge(i,j,-k);
		addedge(j,i,-k);
	}
	scanf("%d",&m);
	while (m--)
	{
		scanf("%d%d",&i,&j);
		for (edge *x=v[i];x;x=x->p)
			if (x->t==j) x->c=-x->c;
		for (edge *x=v[j];x;x=x->p)
			if (x->t==i) x->c=-x->c;
	}
	scanf("%d%d",&A,&B);
	for (i=0;i<=es;i++)
		if (e[i].c<0) e[i].c=0;
	memset(iq,false,sizeof(iq));
	h=t=s=1;
	for (i=1;i<=n;i++)
		d[i]=oo;
	d[A]=0;
	iq[A]=true;
	Q[1]=A;
	while (s)
	{
		k=Q[h];
		for (edge *x=v[k];x;x=x->p)
			if (d[k]+x->c<d[x->t])
			{
				d[x->t]=d[k]+x->c;
				if (!iq[x->t])
				{
					t=(t+1)%M;
					Q[t]=x->t;
					++s;
				}
			}
		iq[k]=false;
		h=(h+1)%M;
		--s;
	}
	printf("%d\n",d[B]);
	return 0;
}