CF402E Strictly Positive Matrix

You have matrix $ a $ of size $ n×n $ . Let's number the rows of the matrix from $ 1 $ to $ n $ from top to bottom, let's number the columns from $ 1 $ to $ n $ from left to right. Let's use $ a_{ij} $ to represent the element on the intersection of the $ i $ -th row and the $ j $ -th column. Matrix $ a $ meets the following two conditions: - for any numbers $ i,j $ ( $ 1

The first line contains integer $ n $ ( $ 2

If there is a positive integer $ k>=1 $ , such that matrix $ a^{k} $ is strictly positive, print "YES" (without the quotes). Otherwise, print "NO" (without the quotes).