#define incpos(p) ( (p).x == cols ? ((p).x = 0, (p).y++, 1) : ((p).x++, 0) )
#define decpos(p) ( (p).x == 0 ? ((p).x = cols, (p).y--, 1) : ((p).x--, 0) )
#define incpos(p) ( (p).x == cols ? ((p).x = 0, (p).y++, 1) : ((p).x++, 0) )
#define decpos(p) ( (p).x == 0 ? ((p).x = cols, (p).y--, 1) : ((p).x--, 0) )