Ferric Ion

有一列n个单元格组成的信息通道，从左至右标号为0至n-1。有一个信息要从最左边传送到最右边的单元格中。每一次你可以从一个单元格向相邻的左或右单元格传送。每一个单元格有一个价格p[i]，如果要传入单元格i，则要花费p[i]，另外，如果p[i]为-1，则表示不可以进入第i格。

题目描述Leopold is indeed a lucky fellow. He just won a huge estate in the lottery. The estate contains several grand buildings in addition to the main mansion, in which he intends to live from now on.

怎么求最短路径数呢？