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fun solution(R: Array<String>): Int {
    val n = R.size
    val m = R[0].length
    
    // 3D array to track visited squares in each direction
    val visited = Array(n) { Array(m) { BooleanArray(4) } }
    
    // Robot starts at (0,0) facing right
    var x = 0
    var y = 0
    var d = 0 // 0: right, 1: down, 2: left, 3: up
    
    // Direction vectors for movement
    val dx = intArrayOf(0, 1, 0, -1)
    val dy = intArrayOf(1, 0, -1, 0)
    
    while (true) {
        // If this direction from (x,y) has been visited, stop
        if (visited[x][y][d]) break
        
        // Mark current cell and direction as visited
        visited[x][y][d] = true
        
        val nx = x + dx[d]
        val ny = y + dy[d]
        
        // If next move is within bounds and is an empty space, move forward
        if (nx in 0 until n && ny in 0 until m && R[nx][ny] == '.') {
            x = nx
            y = ny
        } else {
            // Rotate 90 degrees clockwise
            d = (d + 1) % 4
        }
    }
    
    // Count unique cleaned squares
    var clean = 0
    for (i in 0 until n) {
        for (j in 0 until m) {
            if (visited[i][j].any { it }) clean++
        }
    }
    
    return clean
}