After Napoleon's defeat in 1815, Europe's borders were redrawn at the Congress of Vienna. For the first time since the declaration of independence from Spain in 1581, the Dutch were reunited with the Southern Netherlands in a constitutional monarchy, the United Kingdom of the Netherlands. The union lasted just 15 years. In 1830, a revolution in the southern half of the country led to the de facto independence of the new state of Belgium. The bankrupt Dutch East India Company was liquidated on 1 January 1800, and its territorial possessions were nationalized as the Dutch East Indies.Anglo-Dutch rivalry in Southeast Asia continued to fester over the port of Singapore, which had been ceded to the British East India Company in 1819 by the sultan of Johore. The Dutch claimed that a treaty signed with the sultan's predecessor the year earlier had granted them control of the region. However, the impossibility of removing the British from Singapore, which was becoming an increasingly important centre of trade, became apparent to the Dutch, and the disagreement was resolved with the Anglo-Dutch Treaty of 1824. Under its terms, the Netherlands ceded Malacca and their bases in India to the British, and recognized the British claim to Singapore. In return, the British handed over Bencoolen and agreed not to sign treaties with rulers in the "islands south of the Straits of Singapore". Thus the archipelago was divided into two spheres of influence: a British one, on the Malay Peninsula, and a Dutch one in the East Indies.
Question: How many years after the defeat of Napoleon was the port of Singapore ceded?
Answer: 4