Given the adjacency matrix of an undirected graph with n vertices,

determine and print the number of isolated vertices.

A vertex is isolated if its degree is 0, meaning it is not an endpoint

of any edge (the corresponding row of the adjacency matrix contains

only 0 values).

Input:

The first line contains the natural number n. The following n lines each

contain n binary values, representing the adjacency matrix.

- 1 <= n <= 50

- the matrix is symmetric with 0 on the main diagonal

Output:

The program prints to standard output a single non-negative integer: the number of isolated

vertices in the graph.

Example:

Input:

5

0 1 1 0 0

1 0 0 1 0

1 0 0 0 1

0 1 0 0 0

0 0 1 0 0

Output:

0