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, print_string
let g e c = if e = 1 then f c
let h n c = f @@ String.make n c
let _ = for e = 0 to 1 do g e "L"; h (dy + e) 'U'; h (dx + e) 'R'; g e "D"; g e "R"; h (dy + e) 'D'; h (dx + e) 'L'; g e "U" done