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Famous mathematicians with background in arts/humanities/law etc

What are some examples of mathematicians who had an unconventional education and yet, went on to make an impact on mathematics? Here is an example: Edward Witten. He does not have a formal undergraduate degree in mathematics or physics but won the Fields medal.

More precisely, I am looking for examples of mathematicians whose undergraduate mathematical education was in a different field or was hindered by circumstances like war and poverty or did not have a formal degree as was the case of Srinivasa Ramanujan.