**Step 1: Identify the relevant industry**
Based on the provided facts and the S&P methodologies, "ENI S.P.A." is an integrated oil and gas company. The most appropriate industry methodology is "Oil And Gas Exploration And Production". As per S&P guidelines for this sector, we follow the baseline corporate formulas for calculating Adjusted Debt and Adjusted EBITDA without specific subsector modifications other than standard adjustments (like leases and hybrids).

**Step 2: Estimate Adjusted Debt**
*   Reported Debt = Short-term Borrowings + Current Portion of Long-term Borrowings + Long-term Borrowings
    = 2,299,000,000 + 1,781,000,000 + 23,714,000,000 = 27,794,000,000 EUR
*   Leases = Current Lease Liabilities + Noncurrent Lease Liabilities
    = 948,000,000 + 4,389,000,000 = 5,337,000,000 EUR
*   Pension Deficit = 0 (Not provided in facts)
*   Guarantees = 0 (Not provided in facts)
*   Hybrid Debt Portion = ENI has perpetual subordinated bonds classified in equity. The coupon payments of 138,000,000 EUR suggest a principal value (assuming ~6-7% coupon) around 2,000,000,000 EUR. However, in the absence of an explicit balance sheet liability line item for hybrid debt and lacking specific terms to guarantee full debt equivalence, standard S&P methodology typically requires explicit disclosure to equity-credit hybrids as debt. We will conservatively set this to 0 based strictly on the provided numeric facts.
*   Other debt-like items = 0
*   Eligible Cash = Cash And Cash Equivalents = 8,254,000,000 EUR

Adjusted_Debt = (Reported Debt + Leases) - Eligible Cash
Adjusted_Debt = (27,794,000,000 + 5,337,000,000) - 8,254,000,000
Adjusted_Debt = 33,131,000,000 - 8,254,000,000 = 24,877,000,000 EUR

**Step 3: Estimate Adjusted EBITDA**
*   EBITDA (Reconstructed) = Profit Loss From Operating Activities + Depreciation And Amortisation Expense + Impairment Loss - Write Off Of Tangible And Intangible Assets
    = 17,510,000,000 + 7,205,000,000 + 1,140,000,000 - 599,000,000 = 25,256,000,000 EUR
*   Adjustment for Leases = Estimated Interest Expense on Lease Liabilities (typically ~5% of average lease balance) + Depreciation of Right-of-Use Assets.
    Average Leases = (5,337,000,000 + 4,951,000,000) / 2 ≈ 5,144,000,000 EUR. Estimated Interest ≈ 257,000,000 EUR.
    Depreciation of ROU Assets ≈ Change in ROU + Additions - Write-offs ≈ (4,821,000,000 - 4,446,000,000) + 3,000,000 ≈ 378,000,000 EUR.
    Lease EBITDA adjustment ≈ 257,000,000 + 378,000,000 = 635,000,000 EUR.
*   Nonrecurring items, pension adjustments, JV proportional EBITDA = 0 (Standard baseline unless specified)

Adjusted_EBITDA = EBITDA + Adjustment for Leases
Adjusted_EBITDA = 25,256,000,000 + 635,000,000 = 25,891,000,000 EUR

**Step 4: Calculate Adjusted Debt / Adjusted EBITDA**
Ratio = Adjusted_Debt / Adjusted_EBITDA
Ratio = 24,877,000,000 / 25,891,000,000 ≈ 0.9608

<answer>0.96</answer>