CREATE TABLE table_name_18 (horizontal_bar VARCHAR(255), parallel_bars VARCHAR(255), pommel_horse VARCHAR(255), position VARCHAR(255))
What is the horizontal bar score with a pommel horse of n/a, and the position is less than 27, and the parallel bars score is 15.800?
    
SQL: SELECT horizontal_bar FROM table_name_18 WHERE pommel_horse = "n/a" AND position < 27 AND parallel_bars = "15.800"