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## B. Sea Burial

Time limit: 1.0 second
Memory limit: 64 MB
There is Archipelago in the middle of a shoreless ocean. An ancient tribe of cannibals lives there. Shamans of this race have been communicating with gods and admonishing people for ages. They could generate a rain during a drought and clear the sky in a raining season. A long time ago the first shaman of the tribe jumped into one of the seas and drowned while being in a sacred trance. Since then all the land inside this sea is regarded as sacred. According to an ancient law, all shamans must be buried on a sacred land. However, souls of dead shamans cannot get on with each other, so each shaman must be buried on a separate island. An old prophecy says that if two shamans are buried on the same land, then a dreadful time will come and the tribe will perish.
How many shamans will the tribe outlive? This problem bothered all the chiefs of the tribe who were coming into power. So one of the chiefs ordered to compile a map of Archipelago. The cannibals toiled for a whole year and coped with the task. But the map was too large and complicated to count all the sacred islands. So the tribe's shaman appealed to gods and asked them to help with counting the islands. And the tribe was blessed with a Programmer and a Computer, which came down to earth in a cloud of light and fire. Yes, you are this Programmer, and you are destined to live with these cannibals until you have counted the islands; then you'll be transferred back home. Remember that there may be seas inside islands, and islands inside those seas.

### Input

The first input line contains four integers W, H, X and Y, separated with one or several spaces. 1 ≤ W, H ≤ 500 are respectively the width and the height of the map. 1 ≤ XW and 1 ≤ YH are the coordinates of the point where the first shaman drowned. The next H lines contain description of the map. Each line contains W symbols describing correspondent fragments of the map. Symbol "." stands for a sea fragment and symbol "#" stands for a land fragment. Two fragments belong to the same sea if they are adjacent horizontally, vertically, or diagonally. Two fragments belong to the same island if they are adjacent horizontally or vertically (but not diagonally). Land fragments that are adjacent to the map's border are not considered as islands. Coordinates are counted from the left upper corner.

### Output

The output should contain a single integer, which is the number of the islands inside the sacred sea.

### Samples

inputoutput
```9 7 1 1
........#
.#######.
.#.....#.
.#.#.#.#.
.#.....#.
.#######.
#........
```
```3
```
```9 7 3 3
........#
.#######.
.#.....#.
.#.#.#.#.
.#.....#.
.#######.
#........
```
```2
```
Problem Author: Stanislav Skorb (prepared by Ivan Dashkevich)
Problem Source: Open collegiate programming contest for student teams, Ural State University, March 15, 2003
To submit the solution for this problem go to the Problem set: 1250. Sea Burial