Problem Statement

N participants, numbered 1 to N, will participate in a contest with M problems, numbered 1 to M.
For an integer i between 1 and N and an integer j between 1 and M, participant i can solve problem j if the j-th character of S_i is o, and cannot solve it if that character is x.
The participants must be in pairs. Print the number of ways to form a pair of participants who can collectively solve all the M problems.
More formally, print the number of pairs (x,y) of integers satisfying $1\leq x < y\leq N$ such that for any integer j between 1 and M, at least one of participant x and participant y can solve problem j.

Input

The input is given from Standard Input in the following format:
N M
S_1
S_2
$\vdots$
S_N

Output

Print the answer.

Constraints

• N is an integer between 2 and 30, inclusive.
• M is an integer between 1 and 30, inclusive.
• S_i is a string of length M consisting of o and x.

Sample Input 1

5 5
ooooo
oooxx
xxooo
oxoxo
xxxxx

Sample Output 1

5

The following five pairs satisfy the condition: participants 1 and 2, participants 1 and 3, participants 1 and 4, participants 1 and 5, and participants 2 and 3.
On the other hand, the pair of participants 2 and 4, for instance, does not satisfy the condition because they cannot solve problem 4.

Sample Input 2

3 2
ox
xo
xx

Sample Output 2

1

Sample Input 3

2 4
xxxx
oxox

Sample Output 3

0

见题面 Input 部分

见题面 Output 部分