import java.util.*

fun main(args: Array<String>) {
    val (w, h) = readLine()!!.split(" ").map { it.toInt() }
    val map = (1..h).map { readLine()!!.split(" ").map { it.toInt() } }
    val step = Array(h){ Array(w) { mutableMapOf<Int?, Step>() } }
    val queue = LinkedList<Pos>()
    queue.add(Pos(0,0))
    step[0][0][null] = Step(0, null)
    while (queue.isNotEmpty()) {
        val cur = queue.pop()
        step[cur.r][cur.c].values.forEach { s ->
            val next = listOf(Pos(cur.r-1, cur.c), Pos(cur.r+1, cur.c), Pos(cur.r, cur.c-1), Pos(cur.r, cur.c+1))
            for(n in next) {
                if(n.r !in map.indices) {
                    continue
                }
                if(n.c !in map[n.r].indices) {
                    continue
                }
                if(step[n.r][n.c][map[cur.r][cur.c]]?.step?:200 <= s.step + 1) {
                    continue
                }
                if(s.prev == map[n.r][n.c]) {
                    continue
                }
                if(map[cur.r][cur.c] == map[n.r][n.c]) {
                    continue
                }
                var isValid = false
                s.prev?.let { prev ->
                    val list = listOf(prev, map[cur.r][cur.c], map[n.r][n.c]).sorted()
                    map[cur.r][cur.c].let {
                        if(list[0] == it || list[2] == it) {
                            isValid = true
                        }
                    }
                }?: run { isValid = true }
                if(isValid) {
                    step[n.r][n.c][map[cur.r][cur.c]] = Step(s.step + 1, map[cur.r][cur.c])
                    queue.add(n)
                }
            }
        }
    }
    println(step.last().last().values.firstOrNull()?.step?:-1)
}

data class Step(val step:Int, val prev:Int?)
data class Pos(val r:Int, val c:Int)