# Maximum flow and matchings

# Parking

In a parking lot there are a lot of cars and parking spots and all cars want to drive to a parking spot. Due to the traffic regulations cars may only drive parallel to the boundaries of the parking lot and only at the speed of one square per unit of time.

Usually all cars drive to the nearest available parking spot, but that might turn out badly for some cars. Consider for example the following car park (here '**C**' stands for car, '**P**' for parking spot, '**X**' for wall and '**.**' for empty spot):

`.C.....P.X...`

`XX.......X..P`

`XX.....C.....`

If the car on the bottom drives to its nearest parking spot, the upper left car must drive all the way to the right, taking **13** units of time. If, however, the car on the bottom drives to the parking spot on the right, it will take **6** units of time for both cars to find a parking spot.

Find the minimal amount of time it takes before every car can have a parking spot (assuming that the cars act socially like above). All cars start on an empty spot. Cars are small and any number of them can drive on the same square simultaneously. They can drive over empty spots and parking spots, but not through walls. Each car has to end on a separate parking spot.

#### Input

Consists of multiple test cases. Each test case begins with a line that contains two integers **row** and **column** (1 ≤ **row**, **column** ≤ **50**) - the dimensions of the parking lot. Next **row** lines describe the parking lot as mentioned above. The number of cars and parking spots on each given parking lot is no more than **100**.

#### Output

For each test case print in a separate line the minimal amount of time it takes before every car can have a parking spot. If it is impossible for each car to drive to a parking place, print **-1**. If there is no cars at the parking lot, print **0**.

6 11 XXXXXXXXXXX X......XPPX XC...P.XPPX X......X..X X....C....X XXXXXXXXXXX 3 5 ..X.. C.X.P ..X..

5 -1