Uolevi has bought a rectangle pizza that consists of n \times m cells. For each cell, the topping is given. There are 26 possible toppings, marked with symbols A–Z.

However, the pizza is so large that Uolevi can't eat it entirely. Instead, he will cut a subrectangle and eat it. As a special requirement, Uolevi wants that each cell in the subrectangle has a different topping.

Your task is to calculate the number of possible subrectangles.

Input

The first input line contains two integers n and m.

After this, n lines describe the pizza. Each line contains m characters.

Output

You should output the number of possible subrectangles.

Constraints

• 5 \le n \le 200
• 6 \le m \le 200

Example

Syöte:

5 6
UZEEAA
OMHHQX
YCSAHX
YMZNBC
CEKXHM

Tuloste:

161