A 48-year-old man from Mumbai presents with a 3-day history of productive cough with purulent sputum, fever (38.8°C), and dyspnea. Chest X-ray shows consolidation in the right lower lobe. Sputum Gram stain is performed and shows gram-positive cocci in pairs with an oval or lancet-shaped morphology. Culture on blood agar grows alpha-hemolytic colonies. Optochin sensitivity test is positive. What is the most likely organism?