Cities and roads

In the "Milky Way" galaxy, on the planet "Neptune" there are $n$ cities, some of which are connected by roads. Emperor "Maximus" of the "Milky Way" galaxy has decided to make an inventory of the roads on "Neptune". However, as it turns out, he is not very good at math, so he asks you to count the number of roads.

Input

The first line contains the number $n(0\le n\le 100)$. Each of the next $n$ lines contains $n$ numbers, each either one or zero. If the position $(i,j)$ in the square matrix is one, then the $i$-th and $j$-th cities are connected by a road; if it is zero, they are not connected.

Output

Print the number of roads on the planet "Neptune".

Examples