Louis XI, who enjoyed the effective support of Gaston IV, Count of Foix, had an army of 30,000 men. At the beginning of hostilities in May and June 1465, he attacked the Bourbonnais center of the country. Then he began a race to the capital against the Breton and Burgundian armies. Before they joined forces, the king decided to confront the Burgundian army led by the Count of Charolais. The battle occurred at Montlhery, south of Paris, 16 July 1465. The events of the battle are confused. Both parties claimed the victory. The Count of Charolais remained master of the field. But Louis XI reduced the Burgundian army, then cautiously ordered a strategic retreat during the night, and returned to Paris with a "victorious" army . The king strengthened the capital's faltering authority. However, the king's position weakened after the confrontation, especially as he was unable to prevent the junction, on 19 July, of the Burgundian and Breton armies, soon joined by the Counts of Armagnac and Albret and the Duke of Lorraine. After entering Paris on 18 July, Louis XI organized the defense. The feudal princes besieged Paris. Louis XI left the city on 10 August. He went to Rouen and rallied the royal party, assembled provisions, and returned to Paris on 28 August, with powerful reinforcements. A truce was signed on September 3, which did not prevent the Leaguers from taking Pontoise and Rouen. Fighters on both sides did not quite know how to end the conflict. Louis XI pretended to yield.
Question: How many days was it between when Louis XI left Paris and when he returned to Paris?
Answer: 18