You will be given a definition of a task first, then some input of the task.
In this task, you're given a passage, further information available on a particular linked term from the statement, and a question. Your job is to generate the answer to the question by using the information provided. If there is no clear answer obtainable, output 'none'.

Passage: Van der Lans has a Catholic background. Between 1960 and 1967 he attended a Catholic primary school in Amsterdam (until 1964) and The Hague. Between 1967 and 1973 he attended a Catholic secondary school in The Hague. He attended the atheneum and specialized in sciences. Between 1973 and 1981 he studied psychology at the Catholic University Nijmegen. In 1977 he received his candidate's exam (roughly equivalent to a bachelor's degree) and in 1981 he received his doctoral exam (roughly equivalent to a master's degree. Van der Lans specialized in cultural psychology and Psychology of religion. He also took additional courses in communication studies and education studies. He wrote his doctoral thesis about "Youth Culture, Provo and the Youth Movement" . Between 1979 and 1981 he attended courses to become a teacher in civics and science education. Between 1977 and 1981 he worked as a student-assistant on the faculty of social sciences at different departments. Between 1977 and 1983 he worked as a journalist for the quarterly magazine Psychologie & Maatschappij (Psychology and Society).
Link Information: none Question: What was the population of Amsterdam the year Van der Lans stopped attending Catholic primary school there?
Output:
Answer: none