看一下去重

错误代码：

	sort (a + 1, a + n + 1, [] (node i, node j) {return i.w < j.w;});
	for (int i = 1; i <= n; ++i) {
		while (m && a [i].l > b [m].l) --m;
		b [++m] = a [i];
	}

正确代码

	sort (a + 1, a + n + 1, [] (node i, node j) {return i.w < j.w || i.w == j.w && i.l < j.l;});
	for (int i = 1; i <= n; ++i) {
		while (m && a [i].l >= b [m].l) --m;
		b [++m] = a [i];
	}