Task: Question Answering
Input (English): Passage: In 17th-century Spain, painters rarely enjoyed high social status. Painting was regarded as a craft, not an art such as poetry or music. Nonetheless, Velázquez worked his way up through the ranks of the court of Philip IV, and in February 1651 was appointed palace chamberlain (aposentador mayor del palacio). The post brought him status and material reward, but its duties made heavy demands on his time. During the remaining eight years of his life, he painted only a few works, mostly portraits of the royal family. When he painted Las Meninas, he had been with the royal household for 33 years.
Philip IV's first wife, Elizabeth of France, died in 1644; and their only son, Balthasar Charles, died two years later. Lacking an heir, Philip married Mariana of Austria in 1649, and Margaret Theresa (1651–1673) was their first child, and their only one at the time of the painting. Subsequently, she had a short-lived brother Philip Prospero (1657–1661), and then Charles (1661–1700) arrived, who succeeded to the throne as Charles II at the age of three. Velázquez painted portraits of Mariana and her children, and although Philip himself resisted being portrayed in his old age he did allow Velázquez to include him in Las Meninas. In the early 1650s he gave Velázquez the Pieza Principal ("main room") of the late Balthasar Charles's living quarters, by then serving as the palace museum, to use as his studio. It is here that Las Meninas is set. Philip had his own chair in the studio and would often sit and watch Velázquez at work. Although constrained by rigid etiquette, the art-loving king seems to have had a close relationship with the painter. After Velázquez's death, Philip wrote "I am crushed" in the margin of a memorandum on the choice of his successor.During the 1640s and 1650s, Velázquez served as both court painter and curator of Philip IV's expanding collection of European art. He seems to have been given an unusual degree of freedom in the role. He supervised the decoration and interior design of the rooms holding the most valued paintings, adding mirrors, statues and tapestries. He was also responsible for the sourcing, attribution, hanging and inventory of many of the Spanish king's paintings. By the early 1650s, Velázquez was widely respected in Spain as a connoisseur. Much of the collection of the Prado today—including works by Titian, Raphael, and Rubens—were acquired and assembled under Velázquez's curatorship. 
Question: What is the full name of the person that gave Velázquez the Pieza Principal ("main room") of the late Balthasar Charles's living quarters?
Output (English): Philip IV.