package main

import (
	"bufio"
	"fmt"
	"io"
	"log"
	"os"
)

func main() {
	f := os.Stdin
	if len(os.Args) > 1 && os.Args[1] != "-" {
		var err error
		f, err = os.Open(os.Args[1])
		if err != nil {
			log.Fatal(err)
		}
		defer f.Close()
	}

	grid, err := readDiagram(f)
	if err != nil {
		log.Fatal(err)
	}

	var total int
	for i := 1; ; i++ {
		removed := removePapers(grid)
		total += removed
		fmt.Printf("%2d: removed %d\n", i, removed)
		if removed == 0 {
			break
		}
	}
	fmt.Printf("total %d\n", total)
}

func removePapers(grid [][]bool) (removed int) {
	type position struct {
		x, y int
	}
	var toRemove []position
	for y, row := range grid {
		for x, b := range row {
			if !b {
				continue
			}
			if countAdjacent(grid, x, y) < 4 {
				toRemove = append(toRemove, position{
					x: x,
					y: y,
				})
			}
		}
	}
	for _, pos := range toRemove {
		grid[pos.y][pos.x] = false
	}
	return len(toRemove)
}

func countAdjacent(grid [][]bool, x, y int) int {
	var count int
	xFrom := max(x-1, 0)
	yFrom := max(y-1, 0)
	yTo := min(y+1, len(grid)-1)

	for yi := yFrom; yi <= yTo; yi++ {
		xTo := min(x+1, len(grid[yi])-1)

		for xi := xFrom; xi <= xTo; xi++ {
			if xi == x && yi == y {
				continue
			}
			if grid[yi][xi] {
				count++
			}
		}
	}
	return count
}

func readDiagram(r io.Reader) ([][]bool, error) {
	var grid [][]bool
	sc := bufio.NewScanner(r)
	for sc.Scan() {
		var row []bool
		for _, b := range sc.Bytes() {
			switch b {
			case '@', '.':
				row = append(row, b == '@')
			default:
				return nil, fmt.Errorf("read diagram: unexpected character: %q", sc.Bytes())
			}
		}
		grid = append(grid, row)
	}
	return grid, sc.Err()
}