A 58-year-old man from Mumbai with a history of chronic alcoholism presents with productive cough, fever (38.5°C), and dyspnea for 5 days. Chest X-ray shows consolidation in the right lower lobe. Sputum is sent for Gram stain and culture. The Gram stain reveals gram-positive diplococci with a lancet or flame-shaped morphology, often arranged in short chains. Some organisms are seen within polymorphonuclear leukocytes. What is the most likely causative organism of this patient's pneumonia?