i:.''0:"i/9"
f:10<':
+//(1+i)*&/(f'i;|'f'|'i;+f'+i;|+f'+|i)
*/3#d@>d:#'=(0<)#,/{(9>i)*|/(x;1_'x,'0;0,'-1_'x;1_x,0;0,-1_x)}/(#i;0N)#!#,/i