A girl of 8 months during the examination revealed a loud intense systolic murmur over the whole cardiac area with the epicenter in the III-IV intercostal space to the left of the sternum and systolictrembling; II tone over the pulmonary artery of increased volume. AT - 110/70 mm Hg. Art. Complaint no. During the X-ray examination, the size and shape of the heart shadow are not changed. What is the most likely diagnosis?