PLUSEVI

문제

Mirko is a strange boy so he has written down a square matrix full of ones and zeroes. Now he is interested in how many plusses there are in his matrix. 

A plus is a square such that its side has an odd length greater than 1 and all of its cells are zero, except for the middle row and the middle column: they must be full of ones. For example, in the matrix below there are two plusses, one inside the other: 

00100
00100
11111
00100
00100

How many plusses are there in Mirko’s matrix? 

입력

In the first line there is an integer N (3 ≤ N ≤ 2000), dimension of the square matrix. 

Next N lines represents rows of the matrix. 

출력

In one and only line of output print the number of plusses appearing in the matrix. 

 

5
00100
00100
11111
00100
00100

2

8
00010000
00010000
00010000
11111111
00010000
00010010
00010111
00010010

3