// 查找单入口空闲区域
    var m = 0  // 行
    var n = 0  // 列
    var strings: [[String]] = [] // 矩阵
    var rukou: (Int, Int) = (0,0) // 入口坐标
    var rukouCount = 0 // 入口个数
    func HW2023004() {
        // 测试用例
//        let line = "4 4"
//        strings = [["X","X","X","X"],["X","O","O","X"],["X","O","O","X"],["X","O","X","X"]]
//        let line = "4 5"
//        strings = [["X","X","X","X","X"],["O","O","O","O","X"],["X","O","O","O","X"],["X","O","X","X","O"]]
//        let line = "5 4"
//        strings = [["X","X","X","X"],["X","O","O","O"],["X","O","O","O"],["X","O","O","X"],["X","X","X","X"]]
//        let line = "5 4"
//        strings = [["X","X","X","X"],["X","O","O","O"],["X","X","X","X"],["X","O","O","O"],["X","X","X","X"]]
        
        let line = String(readLine()!)
        while let line = readLine() {
            strings.append(Array(line).map { String($0) })
        }
        let inputArr = line.components(separatedBy: " ").map { Int($0) ?? 0}
        m = Int(inputArr.first!)
        n = Int(inputArr.last!)
        var maxZoo = 0  // 最大区域大小
        var quyu: [[Int]] = [] // 最大区域入口坐标和区域大小集合
        for i in 0..<m {
            for j in 0..<n {
                if strings[i][j] == "O" {
                    strings[i][j] = "X" // 已经统计过的区域设置为X
                    var zuobiao: [[Int]] = [[i,j]]
                    obtainZoo(i, j, &zuobiao)
                    if rukouCount == 1 { // 只有一个入口的区域
                        if maxZoo == zuobiao.count { // 有相同大小的单入口空闲区域，只需大小无需坐标
                            quyu.removeAll()
                        }else if maxZoo < zuobiao.count { // 如果成立，则表示空闲区域增大了
                            // 移除原来所有区域信息
                            quyu.removeAll()
                            // 添加最新的区域信息
                            quyu.append([rukou.0, rukou.1, zuobiao.count])
                            // 更新最大区域大小
                            maxZoo = zuobiao.count
                        }
                    }
                    rukouCount = 0 // 重置入口数量
                    rukou = (0,0)  // 重置入口坐标
                }
            }
        }
        if quyu.count == 1 {
            print("\(quyu[0][0]) \(quyu[0][1]) \(quyu[0][2])")
        }else if maxZoo != 0 {
            print(maxZoo)
        }else {
            print("NULL")
        }
    }
    
    func obtainZoo(_ x: Int, _ y: Int, _ list: inout [[Int]]) {
        // 统计区域边界位置的入口个数及坐标
        if x==0 || x==m-1 || y==0 || y==n-1 {
            rukouCount += 1
            rukou.0 = x
            rukou.1 = y
        }
        if x<m-1 {
            if strings[x+1][y] == "O" {
                strings[x+1][y] = "X" // 已经统计过的置为X，防止重复统计
                list.append([x+1, y])
                obtainZoo(x+1, y, &list)
            }
        }
        if y<n-1 {
            if strings[x][y+1] == "O" {
                strings[x][y+1] = "X" // 已经统计过的置为X，防止重复统计
                list.append([x, y+1])
                obtainZoo(x, y+1, &list)
            }
        }
        if y>0 {
            if strings[x][y-1] == "O" {
                strings[x][y-1] = "X" // 已经统计过的置为X，防止重复统计
                list.append([x, y-1])
                obtainZoo(x, y-1, &list)
            }
        }
    }