import java.io.PrintWriter
import java.util.*

data class Pan(val y: Int, val x: Int, val cnt: Int)

fun main(args: Array<String>) = IO().exec {
    val h = int()
    val w = int()
    val s = Array(h){string()}
    val used = Array(h){IntArray(w)}
    val queue = ArrayDeque<Pan>()
    queue.offer(Pan(0,0,1))
    used[0][0] = 1
    while (queue.isNotEmpty()) {
        val item = queue.poll()!!
        for (next in adjacent4(item.y, item.x, h, w)) if (s[next.first][next.second] == '.' && used[next.first][next.second] == 0) {
            used[next.first][next.second] = item.cnt + 1
            queue.offer(Pan(next.first, next.second, item.cnt + 1))
        }
    }
    if (used[h-1][w-1] == 0) {
        println(-1)
    } else {
        var cnt = 1
        var current = Pan(h - 1, w - 1, used[h - 1][w - 1])
        while (current != Pan(0, 0, 1)) {
            cnt++
            for (next in adjacent4(current.y, current.x, h, w)) if (used[next.first][next.second] == current.cnt - 1) {
                current = Pan(next.first,next.second,current.cnt-1)
                break
            }
        }
        var blocks = 0
        for (y in s.indices) for (x in s[0].indices) if (s[y][x] == '#') blocks++
        println(h*w - blocks - cnt)
    }
}

fun adjacent4(y: Int, x: Int, h: Int, w: Int): List<Pair<Int, Int>> {
    return listOf(Pair(-1, 0), Pair(1, 0), Pair(0, -1), Pair(0, 1)).mapNotNull {
        val ny = y + it.first
        val nx = x + it.second
        if (nx in 0 until w && ny in 0 until h) {
            Pair(ny, nx)
        } else null
    }
}

class IO {
    val printable = 33..126
    val buffer = ByteArray(1024)
    var ptr = 0
    var buflen = 0
    val out = PrintWriter(System.out)
    fun hasNextByte(): Boolean {
        if (ptr < buflen) {
            return true
        } else {
            ptr = 0
            buflen = System.`in`.read(buffer)
            if (buflen <= 0) {
                return false
            }
        }
        return true
    }
    fun readByte(): Byte {
        return if (hasNextByte()) buffer[ptr++] else return -1
    }
    fun hasNext(): Boolean {
        while (hasNextByte() && buffer[ptr] !in printable) ptr++
        return hasNextByte()
    }
    fun string(): String {
        if (!hasNext()) throw NoSuchElementException()
        val sb = StringBuilder()
        var b = readByte()
        while (b in printable) {
            sb.appendCodePoint(b.toInt())
            b = readByte()
        }
        return sb.toString()
    }
    fun long(): Long {
        if (!hasNext()) throw NoSuchElementException()
        var n = 0L
        var minus = false
        var b = readByte()
        if (b == '-'.toByte()) {
            minus = true
            b = readByte()
        }
        if (b !in '0'.toByte()..'9'.toByte()) {
            throw NumberFormatException()
        }
        while (true) {
            if (b in '0'.toByte()..'9'.toByte()) {
                n *= 10
                n += b - '0'.toByte()
            } else if (b == (-1).toByte() || b !in printable) {
                return if (minus) -n else n
            } else {
                throw NumberFormatException()
            }
            b = readByte()
        }
    }
    fun int(): Int {
        val nl = long()
        if (nl !in Integer.MIN_VALUE..Integer.MAX_VALUE) throw NumberFormatException()
        return nl.toInt()
    }
    fun double(): Double {
        return string().toDouble()
    }
    fun print(obj: Any) = out.print(obj)
    fun print(i: Int) = out.print(i)
    fun print(l: Long) = out.print(l)
    fun println(obj: Any) = out.println(obj)
    fun println(i: Int) = out.println(i)
    fun println(l: Long) = out.println(l)
    inline fun exec(block: IO.() -> Unit) {
        block()
        out.flush()
    }
}

Measured memory_bytes: 34460