#include <fstream>
#include <iostream>
#include <vector>

struct position
{
	int x;
	int y;
};

int remove_paper_rolls(std::vector<std::string> &lines)
{
	const position positions[] = {
		{ -1, -1 },
		{ 0, -1 },
		{ 1, -1 },
		{ -1, 0 },
		{ 1, 0 },
		{ -1, 1 },
		{ 0, 1 },
		{ 1, 1 },
	};

	int removed_count = 0;

	std::vector<std::string> new_lines;

	for (int y = 0; y < lines.size(); y++) {
		new_lines.push_back("");

		for (int x = 0; x < lines[y].size(); x++) {
			if (lines[y][x] == '.') {
				new_lines[y].append(".");
				continue;
			}

			int amount = 0;

			for (position pos : positions) {
				int check_x = x + pos.x, check_y = y + pos.y;

				if (check_x < 0 || check_y < 0 || check_x >= lines[y].size() || check_y >= lines.size())
					continue;

				if (lines[check_y][check_x] == '@') amount++;
			}

			if (amount < 4) {
				new_lines[y].append(".");
				removed_count++;
			} else {
				new_lines[y].append("@");
			}
		}
	}

	lines = new_lines;

	return removed_count;
}

int main()
{
	std::ifstream file("input.txt");

	std::vector<std::string> lines;
	std::string line;
	while (getline(file, line)) lines.push_back(line);

	int removed = 0, total_removed = 0;
	do {
		removed = remove_paper_rolls(lines);
		total_removed += removed;
	} while (removed > 0);

	std::cout << total_removed << std::endl;
}