Complete graph - 2

While discussing the personal lives of various villains, we have neglected Count Dooku. In his spare time, Count Dooku enjoys folding origami. He has organized his knowledge of origami as follows: Count Dooku knows $n$ figures, and for some of them, he knows how to obtain one from another with a single fold.

To help beginners, Dooku has developed a special table. The cell $[i,j]$ of the table contains "1" if Count Dooku can obtain figure $j$ from figure $i$ with a single fold, and "0" otherwise.

Initially, Count Dooku holds a clean sheet of paper, which is figure number $x$ according to his system, and he wants to create a crane—figure number $y$.

Find the minimum number of folds required for Count Dooku to obtain the desired figure.

Salida

Print the minimum number of folds required for Count Dooku to make the desired figure. If it is impossible, print "-1".