#!/usr/bin/env kotlin

import java.io.File
import java.util.LinkedList

data class Block (
    var type: Type,
    var seen: Boolean = false,
    var distance: Int = Int.MAX_VALUE
) {
    enum class Type {
        Empty,
        Byte,
    }
}

var cutOff = -1
for (byteCount in 1025..File("input.txt").readLines().count()) {
    val bytes = File("input.txt").readLines().subList(0, byteCount).map { it.split(",").let { s -> s[0].toInt() to s[1].toInt() } }.toSet()
    val grid = (0..70).map { row -> (0..70).map { col ->
        Block(
            type = if (bytes.contains(col to row)) Block.Type.Byte
            else Block.Type.Empty,
        )
    }.toMutableList() }.toMutableList()
    grid[0][0].seen = true
    grid[0][0].distance = 0

    val queue = LinkedList<Pair<Int, Int>>()
    queue.addFirst(0 to 0)

    while (!queue.isEmpty()) {
        // Take one off the queue
        val next = queue.pollLast() ?: break

        // Check if we reached goal
        if (next.first == 70 && next.second == 70) {
            break
        }

        // Add neighbors
        if ((0..70).contains(next.first + 1) && grid[next.first + 1][next.second].let { it.type == Block.Type.Empty && it.distance > grid[next.first][next.second].distance + 1 }) {
            grid[next.first + 1][next.second].seen = true
            grid[next.first + 1][next.second].distance = grid[next.first][next.second].distance + 1
            queue.addFirst(next.first + 1 to next.second)
        }
        if ((0..70).contains(next.second + 1) && grid[next.first][next.second + 1].let { it.type == Block.Type.Empty && it.distance > grid[next.first][next.second].distance + 1 }) {
            grid[next.first][next.second + 1].seen = true
            grid[next.first][next.second + 1].distance = grid[next.first][next.second].distance + 1
            queue.addFirst(next.first to next.second + 1)
        }
        if ((0..70).contains(next.first - 1) && grid[next.first - 1][next.second].let { it.type == Block.Type.Empty && it.distance > grid[next.first][next.second].distance + 1 }) {
            grid[next.first - 1][next.second].seen = true
            grid[next.first - 1][next.second].distance = grid[next.first][next.second].distance + 1
            queue.addFirst(next.first - 1 to next.second)
        }
        if ((0..70).contains(next.second - 1) && grid[next.first][next.second - 1].let { it.type == Block.Type.Empty && it.distance > grid[next.first][next.second].distance + 1 }) {
            grid[next.first][next.second - 1].seen = true
            grid[next.first][next.second - 1].distance = grid[next.first][next.second].distance + 1
            queue.addFirst(next.first to next.second - 1)
        }
    }

    if (grid[70][70].distance == Int.MAX_VALUE) {
        cutOff = byteCount
        break
    }
}

println(File("input.txt").readLines()[cutOff - 1])