How many previous years did Maebashi Ikuei high school have a total number of 1 participation?
create table table_2518850_4 (year_of_previous_participation varchar, total_number_of_participation varchar, high_school_name varchar, PRIMARY KEY (year_of_previous_participation))
select count(year_of_previous_participation) from table_2518850_4 where total_number_of_participation = 1 and high_school_name = "maebashi ikuei"