import java.io.PrintWriter

val pw = PrintWriter(System.out)
fun main(args: Array<String>) {
    func()
    pw.flush()
}
fun print(value: Any) { pw.print(value) }
fun println(value: Any = "") { pw.println(value) }

//ABC129_D
fun func() {
    val (H, W) = listOfInt()
    var S = Array<String>(H) { next() }
    var WW = Array<IntArray>(H) { IntArray(W) }
    var HH = Array<IntArray>(H) { IntArray(W) }
    for (h in 0 until H) {
        var w = 0
        while (w < W) {
            if (S[h][w] == '.') {
                var c = w
                while (c < W && S[h][c] == '.') c++
                val sum = c - w
                while (w < c) WW[h][w++] = sum
            } else w++
        }
    }

    for (w in 0 until W) {
        var h = 0
        while (h < H) {
            if (S[h][w] == '.') {
                var r = h
                while (r < H && S[r][w] == '.') r++
                val sum = r - h
                while (h < r) HH[h++][w] = sum
            } else h++
        }
    }

    var ans = 0
    for (h in 0 until H)
        for (w in 0 until W)
            ans = Math.max(ans, WW[h][w] + HH[h][w] - 1)
    println("${ans}")
}

fun next() = readLine()!!
fun nextInt() = Integer.parseInt(next())
fun listOfString() = next().split(" ")
fun listOfInt() = listOfString().map { Integer.parseInt(it) }
