A 41-year-old male schoolteacher, a nonsmoker, presents with lightheadedness and increased shoness of breath with "lack of stamina" and chest pain. On physical examination, vital signs are normal. The patient is overweight with a BMI of 33. CVS exam reveals a left parasternal heave with a harsh grade 3/6 systolic flow murmur and a loud P2 sound. Chest radiographs are shown below.What is the most likely diagnosis?