#include <iostream.h>

struct node
{
	node* next;
	int time;
};

struct points
{
	int num;
	node* first;
	node* last;

	points()
	{
		num=0;
	}
};

void main(void)
{
	void findtime(points*, int**, int, int, int);
	int meettime(points a, points b);

	int a,i,n,m,p,q,j,k,s,t,l,meet;
	cin>>a;
	for(i=0;i<a;i++)
	{
		cin>>n>>m>>p>>q;
		int** streams = new int*[n];
		for(j=0;j<n;j++)
			streams[j] = new int[n];
		points* timea = new points[n];
		points* timeb = new points[n];
		for(j=0;j<n;j++)
		{
			for(k=0;k<n;k++)
			{
				streams[j][k] = -1;
				if(j==k)
					streams[j][k] = 0;
			}
		}
		for(j=0;j<m;j++)
		{
			cin>>s>>t>>l;
			streams[s-1][t-1]=l;
		}
		timea[p-1].first =new node();
		timea[p-1].first->time=0;
		timeb[q-1].first = new node();
		timeb[q-1].first->time = 0;
		timea[p-1].last = timea[p-1].first;
		timeb[q-1].last = timeb[q-1].first;
		timea[p-1].num++;
		timeb[q-1].num++;
		findtime(timea, streams,p-1,n,0);
		findtime(timeb, streams,q-1,n,0);
		meet = -1;
		int b;
		for(j=0;j<n;j++)
		{
			b=meettime(timea[j],timeb[j]);
			if(b != -1 && (meet == -1 || b < meet))
				meet = b;
		}
		cout << "Data Set " << i +1 << ": Boats can ";
		if(meet == -1)
			cout << "never meet\n";
		else
			cout << "meet at time " << meet << "\n";
	}
}

void findtime(points* time, int** streams, int cur, int n, int t)
{
	int i;
	for(i=0; i < n; i++)
	{
		if(streams[cur][i] > 0)
		{
			if(time[i].num==0)
			{
				time[i].first=new node();
				time[i].first->time = t+streams[cur][i];
				time[i].last=time[i].first;
			}
			else
			{
				time[i].last->next = new node();
				time[i].last->next->time = t + streams[cur][i];
				time[i].last=time[i].last->next;
			}
			time[i].num++;
			findtime(time, streams, i,n,t + streams[cur][i]);
		}
	}
}

int meettime(points a, points b)
{
	int time = -1;
	int i,j, cur;
	node* cura = a.first;
	node* curb;
	for(i = 0; i < a.num; i++)
	{
		curb = b.first;
		for(j = 0; j < b.num; j++)
		{
			if (cura->time == curb->time && (time == -1 || cura->time < time))
				time = cura->time;
			if(j+1 == b.num)
				break;
			curb=curb->next;
		}
		if(i+1 == a.num)
			break;
		cura=cura->next;
	}
	return time;
}