human
Considering the provided database schema and associated query, produce SQL code to retrieve the answer to the query. 
###Database Schema: Masculine a-stems, Masculine u-stems, Feminine ō-stems, Neuter a-stems, Masculine an-stems, Feminine ōn-stems
###Question: What is the masculine u form for the old Swedish word with a neuter a form of skipum?
gpt
SELECT Masculine u-stems FROM table WHERE Neuter a-stems = skipum