object Main {

  object Scanner {
    private val buf = new Array[Byte](1024); private var ptr = 0; private var len = 0
    @inline private def isPrintableChar(c: Int): Boolean = 33 <= c && c <= 126
    @inline private def hasNextByte(): Boolean =
      if (ptr >= len) { ptr = 0; len = System.in.read(buf); len > 0 } else { true }
    @inline private def hasNext(): Boolean = {
      while (hasNextByte() && !isPrintableChar(buf(ptr))) ptr += 1
      hasNextByte()
    }
    @inline private def readByte(): Byte =
      if (hasNextByte()) { val res = buf(ptr); ptr += 1; res } else { -1 }
    def next(): String = {
      if(!hasNext()) ???
      val sb = new StringBuilder; var b = readByte()
      while (isPrintableChar(b)) { sb.append(b.toChar); b = readByte() }
      sb.toString
    }
    def nextInt(): Int = {
      val n = nextLong()
      if (n < Int.MinValue || Int.MaxValue < n) ???
      n.toInt
    }
    def nextLong(): Long = {
      if(!hasNext()) ???
      var minus = false; var b = readByte()
      if (b == '-') { minus = true; b = readByte() }
      def go (b: Byte, n: Long = 0): Long =
        if ('0' <= b && b <= '9') { go(readByte(), n * 10 + b - '0') }
        else if (minus) { -n } else { n }
      go(b)
    }
    def nextDouble(): Double = next.toDouble
  }

  def main(args: Array[String]): Unit = {
    val H, W = Scanner.nextInt()
    val S = Array.fill(H)(Scanner.next())
    val dph = Array.fill[Short](H, W)(-1) // 未計算の場合-1, dp(i)(j)(0) 縦の数 dp(i)(j)(1)横の数
    val dpw = Array.fill[Short](H, W)(-1)
    var i = 0
    while (i < H) {
      var j = 0
      while (j < W) {
        if (S(i)(j) == '.') { // 障害物ではない場合
          if (dph(i)(j) == -1) { // 縦方向未計算の場合のみ計算
            var di = 0
            while (i + di < H && S(i+di)(j) == '.') { // 障害物に当たるか壁に当たるかまで
              di += 1
            }
            var dii = 0
            val hoge = (di - 1).toShort
            while (dii < di) {
              dph(i+dii)(j) = hoge
              dii += 1
            }
          }
          if (dpw(i)(j) == -1) { // 横方向未計算の場合のみ計算
            var dj = 0
            while (j + dj < W && S(i)(j+dj) == '.') { // 障害物に当たるか壁に当たるかまで
              dj += 1
            }
            var djj = 0
            val hoge = (dj - 1).toShort
            while (djj < dj) {
              dpw(i)(j+djj) = hoge
              djj += 1
            }
          }
        }
        j += 1
      }
      i += 1
    }

    var max = 0
    i = 0
    while (i < H) {
      var j = 0
      while (j < W) {
        if (S(i)(j) == '.') { // 障害物ではない場合
          max = Math.max(max, dph(i)(j) + dpw(i)(j) + 1)
        }
        j += 1
      }
      i += 1
    }
    println(max)
  }

}

