Given a simple undirected unweighted graph. Count the number of hanging vertices in it. The vertex is hanging, if its degree is $1$. \InputFile The first line contains number $n~(1 \le n \le 1000)$. The next $n$ lines contain the adjacency matrix. \OutputFile Print the number of hanging vertices in a graph. \includegraphics{https://static.e-olymp.com/content/a2/a2eef5c326fc869babcf1a5ea52db1e4384a0f5b.gif}