Competitions

# Graph representation

# Number of hanging vertices 1

Given a simple undirected unweighted graph. Count the number of hanging vertices in it. The vertex is hanging, if its degree is **1**.

#### Input

The first line contains number **n** (**1** ≤ **n** ≤ **1000**). The next **n** lines contain the adjacency matrix.

#### Output

Print the number of hanging vertices in a graph.

Input example #1

2 0 1 1 0

Output example #1

2

Input example #2

3 0 1 1 1 0 1 1 1 0

Output example #2

0