int k = 1;
	for(int i = 0; i < n; ++i)
	{
		scanf("%d %d %d", &a, &b, &c);
		G[k].w = c; G[k].end = b+1; G[k].next = first[a]; first[a] = k++;
		if(outset > a) outset = a;
		if(destination < b+1) destination = b+1;
	}
	for(int i = outset+1; i <= destination; ++i)
	{
		G[k].w = 0; G[k].end = i; G[k].next = first[i-1]; first[i-1] = k++;
		G[k].w = -1; G[k].end = i-1; G[k].next = first[i]; first[i] = k++;
	}
k值一开始设置为0，和first数组的值一样，导致覆盖掉了一些边，哎。