I'll estimate the FFO / Net Debt ratio for A2A based on S&P methodology.

## Step 1: Calculate FFO (Funds From Operations)

S&P's FFO is essentially:
FFO = Net Income + Depreciation & Amortization + Impairments + Other Non-cash items - Gains on asset sales + adjustments

From the data for 2022 (period 2022-01-01 to 2023-01-01):

- **Profit Loss**: 448 million EUR
- **Depreciation Expense**: 491 million EUR
- **Amortisation Expense**: 233 million EUR
- **Adjustments for Impairment Loss**: 10 million EUR
- **Adjustments for Provisions** (non-cash): 92 million EUR
- **Gains on disposal of noncurrent assets**: -191 million EUR (this was a gain, so we subtract it)
- **Undistributed profits of associates**: -2 million EUR

Alternatively, S&P FFO can be approximated as:
FFO ≈ EBITDA - Net Interest - Taxes paid - Non-controlling interests

- **EBITDA**: 1,505 million EUR
- **Interest Paid**: 75 million EUR (from cash flow statement)
- **Income Taxes Paid**: 201 million EUR
- **Non-controlling interests (cash dividends paid)**: 19 million EUR (dividends to NCI from equity statement)
- **Result from non-recurring transactions**: 157 million EUR (need to consider if this includes gains on disposals)

Using the S&P approach more carefully:
FFO = EBITDA - Net cash interest - Cash taxes - Preferred dividends/minority dividends

FFO ≈ 1,505 - 75 - 201 - 19 = 1,210 million EUR

But we should remove the non-recurring gain on disposals (157M relates to this):
FFO ≈ 1,505 - 157 - 75 - 201 - 19 ≈ 1,053 million EUR

Actually, let me reconsider. The EBITDA of 1,505M already includes the result from non-recurring transactions. Let me check: Operating profit (687) + non-recurring (157) = 844, but EBITDA = 1,505 and D&A = 818, so 1,505 - 818 = 687 = operating profit. The 157M non-recurring seems to be below operating profit.

So EBITDA = 1,505M is clean of the non-recurring item.

FFO = 1,505 - 75 - 201 - 19 = 1,210 million EUR

## Step 2: Calculate Net Debt

Net Debt = Total Financial Liabilities - Cash - Financial Assets

At 2023-01-01 (end of 2022):
- **Non-current financial liabilities**: 5,867 million EUR
- **Current financial liabilities**: 1,022 million EUR
- **Total gross debt**: 5,867 + 1,022 = 6,889 million EUR
- **Cash and cash equivalents**: 2,584 million EUR
- **Other current financial assets**: 14 million EUR
- **Other non-current financial assets**: 70 million EUR

Net Debt = 6,889 - 2,584 - 14 - 70 = 4,221 million EUR

S&P typically uses gross debt minus surplus cash, but a simpler approach:
Net Debt = 6,889 - 2,584 = 4,305 million EUR

Using a more standard approach (subtracting only cash):
Net Debt ≈ 4,305 million EUR

## Step 3: FFO / Net Debt

FFO / Net Debt = 1,210 / 4,305 ≈ 0.281 or about 28.1%

Alternatively with the more conservative net debt (4,221):
FFO / Net Debt = 1,210 / 4,221 ≈ 0.287 or about 28.7%

I'll use the standard approach with net debt = gross financial debt minus cash:

FFO / Net Debt ≈ 1,210 / 4,305 ≈ 0.281

<answer>0.28</answer>