Instructions: This task involves creating answers to complex questions, from a given passage. Answering these questions, typically involve understanding multiple sentences. Make sure that your answer has the same type as the "answer type" mentioned in input. The provided "answer type" can be of any of the following types: "span", "date", "number". A "span" answer is a continuous phrase taken directly from the passage or question. You can directly copy-paste the text from the passage or the question for span type answers. If you find multiple spans, please add them all as a comma separated list. Please restrict each span to five words. A "number" type answer can include a digit specifying an actual value. For "date" type answers, use DD MM YYYY format e.g. 11 Jan 1992. If full date is not available in the passage you can write partial date such as 1992 or Jan 1992. If you find multiple spans, please add them all as a comma separated list. Please restrict each span to five words.
Input: Passage: The Second Goryeo-Khitan War was an 11th-century conflict between the kingdom of Goryeo and the Liao dynasty near what is now the border between China and North Korea. It was the second of the Goryeo-Khitan Wars, with the First Goryeo-Khitan War occurring in 993, the second in 1010, and the third in 1018. When King Seongjong died in 997, Liao invested his successor Wang Song as king of Goryeo . In 1009, he was assassinated by the forces of the general Gang Jo. Using it as a pretext, the Liao attacked Goryeo in the next year. They lost the first battle but won the second one, and Gang Jo was captured and killed. The Liao occupied and burnt the Goryeo capital Kaesong. The Khitan withdrew after Goryeo reaffirmed its tributary relationship with the Khitan.
Question: How many years passed between the deaths of King Seongjong and Wang Song?
Answer type: Number
Output:
12.