To estimate **FFO / Net debt** using an S&P-style approach:

1. **Funds from operations (FFO)** is approximated as:
   - Cash flow from operations before working-capital movements and before cash interest/taxes effects, or more simply from the cash-flow statement:
   - Start with **cash flows from operating activities**:  
     \(1,566.829\) million EUR
   - Remove the positive working-capital contribution:  
     \(574.568\) million EUR
   - This gives a rough FFO estimate:  
     \(1,566.829 - 574.568 = 992.261\) million EUR

   So, estimated **FFO ≈ 992.3 million EUR**.

2. **Net debt** is approximated as financial debt less cash and cash equivalents:
   - Noncurrent financial liabilities: \(5,543.755\) million EUR
   - Current financial liabilities: \(1,705.277\) million EUR
   - Cash and cash equivalents: \(794.824\) million EUR

   Net debt:
   \[
   5,543.755 + 1,705.277 - 794.824 = 6,454.208
   \]
   So, estimated **net debt ≈ 6,454.2 million EUR**.

3. **FFO / Net debt**:
   \[
   \frac{992.261}{6,454.208} = 0.1537
   \]

   Expressed as a percentage, this is approximately **15.4%**.

<answer>15.4</answer>