int bfs()
{
	NODE t_node,node;
	int i,j,k,u,v;
	__int64 tmp;
	/* clear the queue */
	while(!que.empty())
		que.pop();
	SET_NODE(t_node,start,0);
	que.push(t_node);
	relax[start] = 0;
	/* while loop */
	while(!que.empty())
	{
		node = que.top();
		que.pop();
		u = node.v;
		if(node.val > relax[node.v])
			continue;
		if(u == end)
		{
			ans = node.val;
			return 0;
		}
		visit[u] = true;
		for(i = net[node.v]; i != -1; i = edge[i].next)
		{
			v = edge[i].v;
			if(visit[v])
				continue;
			tmp = node.val + edge[i].val;
			if((relax[v] == -1||relax[v] > tmp))
			{
				relax[v] = tmp;
				SET_NODE(t_node,v,tmp);
				que.push(t_node);
			}
		}
	}
	ans = -1;
	return 0;
}