let sx, sy, tx, ty = Scanf.scanf " %d %d %d %d" @@ fun a b c d -> a, b, c, d
let dx, dy, f = tx - sx, ty - sy, String.make
let _ = for e = 0 to 1 do Printf.printf "%s%s%s%s%s%s%s%s" (f e 'L') (f (dy + e) 'U') (f (dx + e) 'R') (f e 'D') (f e 'R') (f (dy + e) 'D') (f (dx + e) 'L') (f e 'U') done