Task: Formula-prediction-context (source dataset: cisco-random)

You are given an table region extracted from a real Excel spreadsheet, which is centered around a cell called "Target Cell" (labeled as "[Target Cell]" shown in the table below). The table region below includes up to 10 rows above/below the Target Cell, and 10 columns to the left/right of the Target Cell. 

Your task is to analyze the table context surrounding the Target Cell, and predict the most likely Excel formula that should go in the Target Cell. If multiple formulas are possible, choose the most reasonable or commonly used based on context.

1. Please follow the standard formula syntax in Excel, e.g. always begins with an equal sign (=).
2. Base your predicted formula on the surrounding table context, e.g., column headers, annotations, and data values in nearby cells.
3. No explanation — just output the formula itself in a JSON format: {"formula": "your_formula_here"}.

Input Excel Snippet in Markdown format:
|    | A                                                                                                                                                                                                                                                                                                                            | B                                                          | C   | D             | E    | F    | G   | H                                                                                               | I                 |
|---:|:-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|:-----------------------------------------------------------|:----|:--------------|:-----|:-----|:----|:------------------------------------------------------------------------------------------------|:------------------|
|  4 | How to use the calculator:                                                                                                                                                                                                                                                                                                   |                                                            |     |               |      |      |     |                                                                                                 |                   |
|  5 | Use the lookup Table 1 to understand TACACS+ log retention(in days) for pre-listed number network devices in your network and for standard hard disk size. You can change the two variables below(Number of sessions per day, Average number of commands/session) that are highlighted with blue font for your sizing needs. |                                                            |     |               |      |      |     |                                                                                                 |                   |
|  6 | Use Table 2 to the right for a more customize calculation of TACACS+ log retention(in days) for varying network device count and custom disk size. There are 4 variables( Disk Size, # of network devices, # of sessions, # of commands) that are highlighted and in blue font. You can optimize them for your sizing needs. |                                                            |     |               |      |      |     |                                                                                                 |                   |
|  7 |                                                                                                                                                                                                                                                                                                                              |                                                            |     |               |      |      |     |                                                                                                 |                   |
|  8 | Number of sessions per day                                                                                                                                                                                                                                                                                                   | 4                                                          |     |               |      |      |     | TACACS+ Log Retention (Device administration using scripts) - custom sizing                     |                   |
|  9 | Number of commands/session                                                                                                                                                                                                                                                                                                   | 10                                                         |     |               |      |      |     | Disk Size (GB)                                                                                  | 200.0             |
| 10 | Message Size/Session (KB)                                                                                                                                                                                                                                                                                                    | 5 kB + Number of commands * 3 kB                           |     |               |      |      |     | # NADs                                                                                          | 30000.0           |
| 11 | Log Size/day                                                                                                                                                                                                                                                                                                                 | Number of devices * Number of sessions/day  * Message size |     |               |      |      |     | # Sessions/day or Admins logins/day                                                             | 4.0               |
| 12 |                                                                                                                                                                                                                                                                                                                              | Log Retention in Number of days                            |     |               |      |      |     | # Commands/session                                                                              | 10.0              |
| 13 | Network devices\Disk size (GB)                                                                                                                                                                                                                                                                                               | 200                                                        | 400 | 600           | 1024 | 2048 |     | MnT Log Allocation(GB)                                                                          | 32.00000000000001 |
| 14 | 500                                                                                                                                                                                                                                                                                                                          | 480                                                        | 959 | [Target Cell] | 2455 | 4909 |     | Message Size/Session/Device (KB)                                                                | 35.0              |
| 15 | 1000                                                                                                                                                                                                                                                                                                                         | 240                                                        | 480 | 720           | 1228 | 2455 |     | Message Size/All sessions/Device (KB)                                                           | 140.0             |
| 16 | 5000                                                                                                                                                                                                                                                                                                                         | 48                                                         | 96  | 144           | 246  | 491  |     | Message Size/All sessions/All Device (KB)                                                       | 4200000.0         |
| 17 | 10000                                                                                                                                                                                                                                                                                                                        | 24                                                         | 48  | 72            | 123  | 246  |     | Total Message Size (GB)/day                                                                     | 4.00543212890625  |
| 18 | 20000                                                                                                                                                                                                                                                                                                                        | 12                                                         | 24  | 36            | 62   | 123  |     |                                                                                                 |                   |
| 19 | 30000                                                                                                                                                                                                                                                                                                                        | 8                                                          | 16  | 24            | 41   | 82   |     | Days Retention                                                                                  | 8.0               |
| 20 | 50000                                                                                                                                                                                                                                                                                                                        | 5                                                          | 10  | 15            | 25   | 50   |     |                                                                                                 |                   |
| 21 | Table 1 - Log retention calculator(in days) based on different number of network devices                                                                                                                                                                                                                                     |                                                            |     |               |      |      |     |                                                                                                 |                   |
| 22 |                                                                                                                                                                                                                                                                                                                              |                                                            |     |               |      |      |     | Table 2 - Customized Log retention calculator for device administration using automated script. |                   |



min_row: 4
max_row: 22
min_col: 1
max_col: 9
target_cell_row_idx: 14
target_cell_col_idx: 4
target_cell_value: 1439
formula: =ROUNDUP((D13*0.8*0.2)/((A14*B8*(5+B9*3))/1024/1024),0)