let n = read_int() in let rec f n i c a=if i<n then f n (i+1) c c^a else a in let a =" "^(f n 0 " ##" "")^"\n" in let b= "#"^(f n 1 " #" "")^"\n" in print_string (a^" "^b^b^b^b^" "^b^a);;

Note that non-ascii characters in the above source code will be escaped (such as \x9f).