A 35-year-old previously well man presents to his GP with 3 days of fever, productive cough and right-sided pleuritic chest pain. He is febrile at 38.5 °C, BP 125/75 mmHg, RR 20 breaths/min, SpO2 95% on room air. Chest examination reveals right lower zone crackles. CURB-65 score is 0. What is the most appropriate initial antibiotic regimen in the community?